222 terms

BIO220 Exam 1:Ch.1-6

Material for Exam 1 in Genetics (BIO220) at AACC
theory of epigenesis
posits that an organism is derived from substances present in the egg that differentiate into adult structures during embryonic development
theory of preformation
stated that sex cells contain a complete miniature adult, perfect in every form, called a homunculus
cell theory
all organisms are composed of basic units called cells, which are derived from similar preexisting structures
idea of spontaneous generation
disproved idea of the creation of living organisms from nonliving components
idea of fixity of species
disproved notion that animal and plant groups have remained unchanged in form since the moment of their appearance on Earth
theory of natural selection
based on the observation that populations tend to consist of more offspring than the environment can support, leading to a struggle for survival among them. Those organisms with heritable traits that allow them to adapt to their environment are better able to survive and reproduce than those with less adaptive traits.
chromosome theory of inheritance
the idea put forward independently by Walter Sutton and Theodore Boveri that chromosomes are carriers of genes and the basis for the Mendelian mechanisms of segregation and independent assortment
branch of biology concerned with the study of heredity and variation
diploid (2n)
a condition in which each chromosome exists in pairs; having two of each chromosome
homologous chromosomes
chromosomes that synapse or pair during meiosis and that are identical with respect to their genetic loci and centromere placement (usually one maternal and one paternal in a set)
a form of cellular reproduction producing two progeny cells, identical genetically to the progenitor cell, that is, the production of two cells from one, each with the same chromosome complement as the parent cell
the process of cell division in gametogenesis or sporogenesis during which the diploid number of chromosomes is reduced to the haploid number
haploid (n)
a cell or organism having one member of each pair of homologous chromosomes. Also, the gametic chromosome number
any heritable change; source of all genetic variation
alternative forms of a gene
different observable features produced by different alleles
set of alleles for a given trait carried by an organism
bacteriophages (or phages)
a virus that infects bacteria, using it as the host for reproduction
building blocks of nucleic acids; a single phosphate linked to the 5' carbon of the ribose or deoxyribose sugar linked to a nitrogenous base
nitrogenous bases and pairing in DNA (4)
adenine, guanine, thymine, cytosine; A with T and C with G
process in which the nucleotide sequence in one strand of DNA is used to construct a complementary RNA sequence
messenger RNA; an RNA molecule transcribed from DNA and translated into the amino acid sequence of a polypeptide
synthesis of proteins under the direction of mRNA
polymers made up of amino acid monomers
Number of different amino acids commonly found in proteins?
genetic code
the deoxynucleotide triplets that encode the 20 amino acids or specify termination of translation
a triplet of nucleotides that specifies a particular amino acid or a start or stop signal in the genetic code. 61 codons specify the amino acids used in proteins, and three codons, called stop codons, signal termination of growth of the polypeptide chain
transfer RNA; recognize the information encoded in the mRNA codons and carry the proper amino acids for construction of the protein during translation
central dogma of genetics
DNA makes RNA which most often makes protein
molecules that serve as biological catalysts, essentially causing biochemical reactions to proceed at rates necessary for sustaining life; largest category of proteins
restriction enzymes
cut any organism's DNA at specific nucleotide sequences, producing a reproducible set of fragments
In recombinant DNA, an agent such as a phage or plasmid into which a foreign DNA segment will be inserted and utilized to transform host cells
recombinant DNA
a DNA molecule formed by joining two heterologous molecules
identical molecules, cells, or organisms derived from a single ancestor by asexual or parasexual methods
complete haploid DNA content of a specific organism
commercial and/or industrial processes that utilize biological organisms or products
transgenic animals
animals that contain genes transferred from other animals, usually from a different species
DNA microarrays
an ordered arrangement of DNA sequences or oligonucleotides on a substrate (often glass)
gene therapy
the insertion of working copies of a gene into the cells of a person with a genetic disorder in an attempt to correct the disorder
the study of genomes (genomes-->the complete haploid DNA content of a specific organism)
the study of the expressed proteins present in a cell at a given time
the design and application of software and computational methods for the storage, analysis, and management of biological information such as nucleotide or amino acid sequences
model organisms
organisms used for the study of basic biological processes
a specialized reproductive cell with a haploid number of chromosomes
produced by some bacteria, plants, and invertebrates, a unicellular body or cell encased in a protective coat. It is capable of surviving in unfavorable environmental conditions and gives rise to a new individual upon germinations. In plants, spores are the haploid products of meiosis
the complex of DNA, RNA, histones, and nonhistone proteins that make up uncoiled chromosomes, characteristic of the eukaryotic interphase nucleus
plasma membrane
a phospholipid bilayer that surrounds a cell and serves as a barrier between the cell and its surroundings
cell wall
A protective layer external to the plasma membrane in plant cells, bacteria, fungi, and some protists. In plant cells, the wall is formed of cellulose fibers embedded in a polysaccharide-protein matrix
covering over the plasma membrane, consisting of glycoproteins and polysaccharides, on most animal cells
organisms having true nuclei and membranous organelles and whose cells demonstrate mitosis and meiosis
the membrane-bound cytoplasmic organelle of eukaryotic cells that contains the chromosomes and nucleolus
in prokaryotes, a DNA molecule containing the organism's genome; in eukaryotes, a DNA molecule complexed with RNA and proteins to form a threadlike structure containing genetic information arranged in a linear sequence and visible during mitosis and meiosis
the nuclear site of ribosome biosynthesis and assembly; usually associated with or formed in association with the DNA comprising the nucleolar organizer region
nucleolus organizer region (NOR)
areas of DNA that encode rRNA
prokaryotic cells
organisms lacking nuclear membranes and true chromosomes
area where genetic material is present in prokaryotic cells
nonparticulate, colloidal material referred to as the cytosol, which surrounds and encompasses the cellular organelles
endoplasmic reticulum (ER)
a membranous organelle system in the cytoplasm of eukaryotic cells. In rough ER, the outer surface of the membranes is ribosome-studded; in smooth ER, it is not
generate large amounts of ATP; found in both plant and animal cells
a self-replicating cytoplasmic organelle containing chlorophyll
endosymbiotic theory
the proposal that self-replicating cellular organelles such as mitochondria and chloroplasts were originally free-living organisms that entered in to a symbiotic relationship with nucleated cells
a cytoplasmic organelle composed of nine groups of microtubules, generally arranged in triplets. Centrioles function in the generation of cilia and flagella and serve as foci for the spindles in cell division
spindle fibers
cytoplasmic fibrils formed during cell division that are involved with the separation of chromatids at the anaphase stage of mitosis and meiosis as well as their movement toward opposite poles in the cell
the specialized heterochromatic chromosomal region at which sister chromatids remain attached after replications, and the site to which spindle fibers attach to the chromosome during cell division. Also known as the primary constriction
Classifications of chromosomes based on centromere location (4)
Arms of chromosomes (2)
-p arm (think "petite") is shorter and shown on top
-q arm is longer and is shown below (think "q" is the letter after "p")
the chromosome complement of a cell or an individual. Often used to refer to the arrangement of metaphase chromosomes in a sequence according to length and centromere position
sister chromatids
replica chromatids (two parts of each chromosome) that are connected by a common centromere
locus (pl., loci)
the site of place on a chromosome where a particular gene is located
biparental inheritance
one member of each homologous pair of chromosomes is derived from the maternal parent and one is derived from the paternal parent
sex chromosome
a chromosome, such as X or Y in humans, or Z or W in birds, which is involved in sex determination
single-celled fertilized egg
nuclear division
cytoplasmic division
cell cycle
events that occur from the completion of one division until the beginning of the next division
interphase stage of the cell cycle
interval between divisions
S phase
period during interphase during which replication of the DNA of each chromosome occurs
Stages of Interphase (4)
1) G1-Gap 1
2) [G0 stage-cells can withdraw from the cell cycle during G1]
3) S phase
4) G2-Gap 2
Events of Prophase in Mitosis (3)
1) chromosomes coil up and condense
2) centrioles divide and move apart
3) nuclear envelope breaks down and nucleolus disintegrates
area of differentiated cytoplasm just outside of the nuclear envelope where centrioles are found
Events of Prometaphase in Mitosis (3)
1) Chromosomes are clearly double structures
2) Centrioles reach the opposite poles
3) spindle fibers form
Events of Metaphase in Mitosis (1)
Centromeres align on metaphase plate
metaphase plate
equatorial plane; midline region of the cell
a fibrous structure with a size of about 400 nm, located within the centromere. It appears to be the site of microtubule attachment during division
Events of Anaphase in Mitosis (1)
Centromeres split and daughter chromosomes migrate to opposite poles
daughter chromosome
name for chromatids after initiation of anaphase; formerly sister chromatids
Events of Telophase in Mitosis (6)
1) Daughter chromosomes arrive at poles
2) Cytokinesis commences
late telophase:
3) chromosomes uncoil to chromatin
4) nuclear envelope reforms
5) spindle fibers disappear
6) nucleolus begins to reform
cell plate
cell wall that is synthesized and laid down across the metaphase plate region during telophase in plant cells; becomes the middle lamella
cell furrow
complete constriction of the cell membrane in animal cells
cell division cycle (cdc) mutations
a class of cell division cycle mutations in yeasts that affect the timing and progression through the cell cycle
crossing over
genetic exchange between members of each homologous pair of chromosomes
Difference in behavior of homologous pairs in mitosis and meiosis?
In mitosis, homologous pairs of chromosomes behave autonomously during division; In meiosis, they form pairs and synapse
synapsed structure including a homologous pair of chromosomes in zygotene (2nd) stage of meiosis prophase I; both members of each bivalent have replicated but the double structure is not yet visually apparent
synapsed structure including a homologous pair of chromosomes that appears in pachytene (3rd) stage of meiosis prophase I, after the double structure of each homolog is evident
reductional division
number of centromeres is reduced by one-half; meiosis I
the products of tetrad separation or disjunction at meiotic prophase I; each dyad consists of two sister chromatids joined at the centromere
equational division
number of centromeres remains equal; meiosis II and mitosis
the one chromosome left in each cell at the end of meiosis II after a dyad splits
the pairing of homologous chromosomes at meiosis
Five Substages of Meiotic Prophase I
1) Leptotene stage
2) Zygotene stage
3) Pachytene stage
4) Diplotene stage
5) Diakenesis
Events during Leptotene Stage of Meiotic Prophase I (2)
1) Chromatin material begins to condense, and the chromosomes, though still extended, become visible
2) Chromomeres (localized condensations) are found along each chromosome
Events during Zygotene Stage of Meiotic Prophase I (4)
1) Chromosomes continue to shorten and thicken
2) Homology search occurs
3) Synaptonemal complex begins to form
4) Paired homologs are in the form of bivalents
Events during Pachytene Stage of Meiotic Prophase I (3)
1) Chromosomes continue to coil and shorten
2) Further development of the synaptonemal complex occurs
3) The double structure of each homolog is evident and paired homologs are in the form of tetrads
Events during Diplotene Stage of Meiotic Prophase I (2)
1) Within each tetrad, each pair of sister chromatids begins to separate
2) Earlier crossing over is evident through chiasmata
chiasma (pl., chiasmata)
area where nonsister chromatids remain in contact, thought to represent a point where genetic exchange occurred through the process of crossing over
Events during Diakenesis of Meiotic Prophase I (4)
1) Chromosomes pull farther apart but non sister chromosomes remain loosely associated through chiasmata
2) Terminalization occurs--chiasmata move towards the end of the tetrad
3) Nucleolus and nuclear envelope break down
4) two centromeres of each tetrad attach to the recently formed spindle fibers
the separation of chromosomes during the anaphase stage of cell division
a cell division error in which homologous chromosomes (in meiosis) or the sister chromatids (in mitosis) fail to separate and migrate to opposite poles; responsible for defects such as monosomy and trisomy
production of male gamete
production of female gamete
undifferentiated diploid germ cell
primary spermatocyte
enlarged spermatogonium
secondary spermatocyte
product of first meiotic division in spermatogenesis
product of second meiotic division in spermatogenesis
series of developmental changes that occur to spermatids
sperm; product of spermiogenesis
ova (sing., ovum)
diploid germ cell
primary oocyte
enlarged oogonium
first polar body
one of the products of meiosis I in oogeneis - contains half the chromosomes but little of the cytoplasm
secondary oocyte
product of first meiotic division in oogenesis
product of second meiotic division in oogenesis
second polar body
a small body containing the chromosomes discarded during the second meiotic division of an ovum
folded-fiber model
a model of eukaryotic chromosome organization in which each sister chromatid consists of a single chromatin fiber composed of double-stranded DNA and proteins wound like a tightly coiled skein of yarn
asexual reproduction
reproduction that does not involve the union of gametes and in which a single parent produces offspring that are genetically identical to the parent
chromosomes other than the sex chromosomes. In humans, there are 22 pairs of autosomes.
binary fission
the division of a prokaryotic cell into two offspring cells
organisms having true nuclei and membraneous organelles and whose cells demonstrate mitosis and meiosis
process in sexual reproduction in which male and female reproductive cells join to form a new cell
production of gametes
germ cells
the only cells that can undergo meiosis--spermatogonium & oogonium
two chromosomes that code for the same traits as itself; traits are same, but actual genes may be different
the chromosome complement of a cell or individual. Often used to refer to the arrangement of metaphase chromosomes in a sequence according to length and centromere position.
mitotic spindle (apparatus)
the framework of microtubules that appears in cell division, and eventually attaches to and moves the chromatids apart
specialized structure that performs important cellular functions within a eukaryotic cell
organisms lacking nuclear membranes and true chromosomes
somatic cells
all cells other than the germ cells or gametes in the organism
sperm cells
male reproductive cells
synaptonemal complex
an organelle consisting of a tripartite nucleoprotein ribbon that forms between the paired homologous chromosomes in the pachytene stage of the first meiotic division. May be essential for crossing over.
a cross between an individual whose genotype at one or more loci may be unknown and an individual who is homozygous recessive for the gene or genes in question
X-linked alleles
genes located on the X chromosome
Classification of chromosomes in a karyotype
1) size
2) banding pattern
3) centromere location
Summary of events of 5 periods of prophase I of meiosis
1) leptonena -- chromomeres (localized condensations)
2) zygonema -- bivalents
3) pachynema -- tetrad
4) diplonema -- chiasma
5) diakinesis -- terminalization (chiasmata move toward ends of tetrads)
a term referring to the basic chromosome set or to multiples of that set
2 major differences btwn mitosis & meiosis
1) mitosis produces 2 diploid daughter cells; meiosis produces 4 haploid daughter cells
2) mitosis produces daughter cells that are genetically identical; meiosis produces daughter cells that are not genetically identical
3 ways chromosomes of a karyotype are classified
1) size
2) banding pattern
3) centromere location
nuclear division
different versions of the same gene
an individual with two identical alleles
an individual with two different alleles
the specific allele composition of an individual
the outward appearance of an individual
What information do you get from the Punnett Square? (4)
1) predicted phenotypic ratio
2) predicted genotypic ratio
3) the gametes that each parent can form
2 reasons that the pea plant was a good choice to study
1) existed in several varieties with distinct characteristics
2) structure allowed for easy crosses where the parents could be controlled
true breeding
Mendel's Law of Segregation
during gamete formation, the paired unit factors (alleles) segregate randomly so that each gamete receives one or the other with equal likelihood (50% chance of each)
Mendel's Law of Independent Assortment
during gamete formation, segregating pairs of unit factors (alleles) assort independently of each other (maternal & paternal don't all go to the same side)
chi square test
statistical test to test the null hypothesis that an observed set of data is equivalent to a theoretical expectation
dihybrid cross
a genetic cross involving two characteristics in which the parents possess different forms (traits) of each character
the expression of a trait in the heterozygous condition
specialized reproductive cell with a haploid number of chromosomes
degrees of freedom
F1 generation
first filial generation; the progeny resulting from the first cross in a series
F2 generation
second filial generation; the progeny resulting from a cross of the F1 generation
fertilization of one plant by pollen from a different plant
fertilization in which both egg and pollen come from the same plant
forked-line method
breaks down multi-hybrid crosses into a series of monohybrid crosses- product rule is then applied to line of genotypes; method to solve independent assortment problems
parental generation
The individuals that mate in a genetic cross. Their offspring are the first filial (F1) generation.
offspring of crosses between parents with different traits
loss-of-function allele
a mutation that causes the diminution of a specific wild-type function
3 math operations to calculate probability?
1) sum rule
2) product rule
3) binomial expansion equation
Calculate # of possible gamete types
= # possible alleles ^ # of genes
pedigree analysis
commonly used to determine the inheritance pattern of human genetic diseases
ratio of the frequency of a given outcome to the frequency of all possible outcomes
product rule
the probability that 2 or more independent events will occur is equal to the product of their respective probabilities (this AND that occurs)
sum rule
the probability that 1 of 2 or more mutually exclusive events will occur is the sum of their respective probabilities (this OR that occurs)
binomial expansion
represents all of the possibilities for a given set of unordered events; ex. "What is the probability that two of a heterozygous couple's five children will have blue eyes?"
goodness of fit
how close the observed data are those predicted from a hypothesis
random sampling error
the deviation between observed and expected outcomes
an allele whose potential genetic expression is overridden in the heterozygous condition by a dominant allele
the separation of maternal and paternal homologs of each homologous chromosome pair into gametes during meiosis
monohybrid cross
a genetic cross involving only one character
a group of organisms with common ancestry that has physiological or morphological characteristics of interest for genetic study or domestication
any detectable phenotypic variation of a particular inherited trait
when the expression of one gene or gene pair masks or modifies the expression of another gene or gene pair
essential gene
it is for something that is essential to life, so it will be a lethal gene if it is non-functional
extranuclear inheritance
mitochondrial and chloroplast DNA
gene dosage effect
The gene dosage effect refers to the relationship between the number of functioning copies of a gene and the amount of gene product produced. In order for full deficiency to occur, both alleles must be abnormal
gene interaction
production of novel phenotypes by the interaction of products of alleles of different genes
genetic anticipation
the phenomenon in which the severity of symptoms in genetic disorders increases and the age of onset decreases from generation to generation. It is caused by the expansion of trinucleotide repeats within or near a gene
heterozygote advantage
also called over dominance; the phenomenon in which heterozygote is more vigorous than both the corresponding homozygotes
the process by which the expression of a gene depends on whether it has been inherited from a male or a female parent
incomplete dominance
expressing a heterozygous phenotype that is distinct from the phenotype of either homozygous parent (not blending because you can get back to homozygous in later generations)
incomplete penetrance
Dominant alleles that are not always expressed, often for unknown reasons.
lethal allele
recessive, lethal in homozygous, may produce distinct phenotype when heterozygous, example: yellow coat color in mice
2 components of simple Mendelian inheritance
1) a single gene with two different alleles
2) alleles display a simple dominant/recessive relationship
2 laws of Mendelian inheritance
1) law of segregation
2) law of independent assortment
mutant alleles
an allele that has been altered by mutation
also called heterozygote advantage; heterozygotes have higher fitness than either homozygote
the control of more than one phenotypic characteristic by a single gene
the existence of two or more discontinuous, segregating phenotypes in a population
sex-influenced inheritance
phenotypic expression that is conditioned by the sex of the individual
sex-limited traits
a trait that is expressed in only one sex even though the trait may not be X-linked
temperature-sensitive conditional allele
a conditional mutation that produces a mutant phenotype at one temperature range and a wild-type phenotype at another
wild-type allele
the most common observed , designated as the norm or standard
2 reasons heterozygote displays wild-type phenotype
1) 50% of the normal protein is enough to accomplish the protein's cellular function
2) the heterozygote may actually product more than 50% of the functional protein ("up-regulated")
ex. of incomplete dominance
pink 4 o'clock flower
ex. of incomplete penetrance
60% of heterozygotes carrying a dominant allele exhibit the trait allele-->the trait has 60% penetrance
ex. of expressivity
a polydactyl person with a single extra finger has lower expressivity than a one with several extra fingers
ex. of environmental effect
as temperature increases, the number of eye facets on the drasophilia increase
ex. of overdominance/heterozygote advantage
heterozygotes for the sickle cell allele are more resistant to malaria
ex. of multiple alleles (in population)
rabbit coat color (C, cch, ch, c)
ex. of temperature-sensitive conditional allele
siamese cats
ex. of lethal gene
yellow coat color in mice is dominant phenotypically but recessive lethal (1 will make it yellow; 2 will kill it)
ex. of epistasis
Bombay phenotype in which the FUT1 locus masks the expression of the IA and IB locus
complementation test
a genetic test to determine whether or not two mutations occur within the same gene
ex. of complementation
2 wingless flies have mutations on separate genes-->offspring have wings
2 wingless flies have two different mutations on the same gene-->offspring are wingless
ex. of sex-influences traits
pattern baldness in humans (baldness is dominant in males but recessive in females)
ex. of sex-limited traits
breast development in females
beard growth in males
What is a good indication of a gene interaction?
deviations from the 9:3:3:1 ratio
ex. of codominance
alleles IA & IB for red blood antigens
condition in which the phenotypic effects of a gene's alleles are fully and simultaneously expressed in the heterozygote