Terms in this set (70)
The genetic material on a chromosome that contains the instructions for creating a particular trait, and since the formula is described by a genetic code, a gene is often said to code for a trait
Basic unit that is composed of DNA located on chromosomes
One of the several varieties of a gene such as flower color (purple vs white)
Can be dominant or recessive
The location on a chromosome where a gene is located and every gene has a unique locus on a particular chromosome
A pair of chromosomes that contains the same genetic information, gene for gene, contributed from each parent
What are Mendel's two major discoveries?
1. Law of segregation - segregation of alleles and their chromosomes to individual gametes, where one member of each chromosome pair migrates to an opposite pole so that each gamete contains only one copy of each chromosome and each allele
2. Law of independent assortment - independent assortment of alleles and their chromosomes. The process is independent because the migration of homologues within one pair of homologous chromosomes to opposite poles does not influence the migration of homologues to other pairs
What is the difference between the law of segregation and law of independent assortment?
They both refer to the separation of homologous chromosomes during meiosis. The difference is that law of segregation is basically "when we form gametes we separate our allele copies so gametes are haploid" and law of independent assortment says "the separation of each pair of chromosomes is completely independent from the separation of any other pair - they each separate at random, outcome of one doesn't affect others".
What are the types of generations?
P - parental
F1 - filial - daughter of P
F2 - filial - daughter of F1
Hallmarks the disappearance of silent recessive phenotype in the F1 generation and subsequent reappearance in 25% of individuals
Incomplete dominance, example?
Blending of expressions of alleles, an example is snapdragons that can lead to a pink from a white and red parents
Both inherited alleles are complete expressed. An example is blood types A and B or both can show up as AB if expressed
Multiple alleles, example?
When a trait has more than 2 possible alleles, such as blood type (A, B, AB, O)
one gene affects phenotypic expression of 2nd gene. An example is fur color in dogs.
Pigmentation, where one gene controls (turns on / off) the production of the pigment and the second gene controls color or amount. If 1st gene codes for no pigment -> 2nd gene has no effect
the interaction of many genes to shape a single phenotype w/ continuous variation (height, skin color).
single gene has more than 1 phenotypic expression (gene in pea plants that expressed seed texture also influences phenotype of starch metabolism and water uptake; sickle cell anemia leads to different health conditions); the shape of pea plants affects their metabolism
two or more genes that reside on the same chromosomes and thus cannot separate independently because they are physically connected (inherited together).
The farther apart two linked alleles are on a chromosome, the more often the chromosome will break between them. These genes don't follow the probability rule and expected results from a dihybrid cross
mapping of linkage genes with each map unit being equal to 1% recombination
How often do linked genes exhibit recombination?
18% of the time
refers to single gene resides on sex chromosome; when male (XY) receives an X from mother, whether it is dominant or recessive will be expressed because there is no copy on the Y chromosome.
Most sex linked traits are found on the ____ chromosome
X -> X-linked
can be influenced by sex of individual carrying trait (e.g. Bb female not bald, Bb male is
probability an organism with a specific genotype will express a particular phenotype
term describing the variation of phenotype for a specific genotype
Linkage map vs cytological map
Linkage - portrayal of the sequence of genes on a chromosome
Cytological - requires additional experimental analyses
cannot form blood clot. XHXh is a normal carrier. But if XH is inactivated => Xh is expressed
Sex-linked, recessive gene in humans and can die from minor injuries by bleeding to death (cannot form blood clots)
Much more common in males because it's sex-linked
all chromosomes undergo meiotic nondisjunction and produce gametes with twice the number of chromosomes. Common in plants.
genome with extra/missing chromosome <= often caused by nondisjunction (Down syndrome = trisomy 21).
fraction of body cells have extra or missing chromosome
single nucleotide changes causing substitution, insertion, deletion (latter 2 could cause frameshift).
Purine to purine or pyrimidine to pyrimidine
purine to pyrimidine or vice versa
What can cause a frameshift mutation?
Insertion or deletion
Turner Syndrome results from what?
Nondisjunction of sex chromosomes. (X) Female have only a single X chromosome resulting from nondisjunction
(XXY) offspring (male) have an extra X chromosome resulting from nondisjunction
What is a chromosomal aberration?
Chromosome segments are changed
Chromosome segment is repeated on the same chromosome
Chromosome segments are rearranged in reverse orientation
Segment is moved to another chromosome, and it could be reciprocal (they swap) or Robertsonian (one chromosome from a pair becomes attached to another from a pair, such as chromosome 21 becoming attached to 14 -> down)
spontaneous or induced (mutagenic agents, Xrays)
What are some examples of mutagenic agents?
cosmic rays, Xrays, UV rays, radioactivity, chemical compounds include colchicine (inhibits spindle formation causing polyploidy), mustard gas. Mutagenic agents are generally also carcinogenic
What is the difference between an oncogene and a proto-oncogene?
The latter is a normal gene, stimulating normal growth, but if mutated, it could become an oncogene and lead to cancer
Does Turner's typically cause mental retardation?
aka phenylketonuria is the inability to produce a proper enzyme for phenylalanine breakdown and so the degradation product called phenylpyruvic acid accumulates
Cannot consume things with aspartme
Cannot metabolize phenylalanine into tyrosine
Lack of phenylalaline hydrolase
Fluid build up in tracts
Lysosome defect, and can't breakdown lipids for normal brain function
Defective hemoglobin due to a swap of valine for glutamic acid - single base pair substitution
The normal round cells are swapped for crescent shaped, carrying less oxygen. The good thing though is that their symptoms for malaria are less
Degenerate nervous system disease
Cri du Chat
Deletion on chromsome 5
Forward vs backwards mutation
Forward - already mutated organism mutates again even more and backward - back to original
extranuclear genes are found in mitochondria and chloroplasts. Defects in mito DNA can reduce cell's ATP production. Mitochondria passed to zygote all come from mother, so all related diseases are mother inherited. Note that mitochondria have their own ~70S ribosomes that make mitochondrial proteins w/in mitochondrial matrix!
What types of populations are most susceptible to genetic drift?
An X chromosome that is condensed and visible; dark staining body
In every female cell, one X chromosome is activated and another is deactivated during embryonic development (randomly chosen). So every tissue in the adult female has one X chromosome that remains condensed and inactivate, and this is replicated and passed onto daughter well
Are all cels in a female mammal functionally identical? Why?
No, because of x-inactivation where only genes on one X chromosome will be expressed and the other is inactivated and isn't expressed similarly
Calico cats are an example of what? What happens?
X-inactivation - production of different patches of color in an individual calico cat. The yellow and black colors are determined by a gene on the X chromosome (white is by a different gene)
When the X chromosome with the yellow is inactivated, the black color allele on the active chromosome is expressed, and the hair is black. In other patches, the chromosome with the black allele may be inactivated, and those patches will be yellow
What would be the situation that a female carrier for hemophilia expresses the same traits as a male?
When there is X-inactivation, and the XH dominant is inactivated
Why are fruit flies ideal?
Reproduces often / short life cycle
Reproduces in large numbers / large sample size
Its chromosomes are large and easily recognizable
Its chromosomes are few (4 pairs, 2N = 8)
Mutations occur relatively frequently
Any chromsome that isn't a sex chromosome - humans have 22 pairs
Where is the single circular chromosome of bacteria located in the cell?
A type of plasmid (small circular ring of DNA) that are capable of integration into bacterial genome
How do bacterial cells reproduce?
Binary fission, proliferate very rapidly under favorable conditions. This is an asexual process
What are the three mechanisms that bacteria have for genetic variance?
Process by which a foreign chromosome fragment (plasmid) is incorporated into the bacterial chromosome via recombination, creating new inheritable genetic combinations
Sexual mating in bacteria - transfer of genetic material between two bacteria that are temporarily joined. A cytoplasmic conjugation bridge is formed between the two cell and genetic material transferred from a donor male (+) to a female (-). Only bacteria containing plasmids called sex factors are capable of conjugating
What is the best studied sex factor?
F factor in E.coli
F+ have it
F- dont have it
What does Hfr cells mean?
Sometimes the sex factor becomes integrated into the bacterial genome, and during conjugation, the entire bacterial chromosome replicates and begins to move from the dono cell into the recipient cell. The conjugation bridge usually breaks before the entire chromosome is transferred, but the bacterial genes that enter the recipent cell can easily recombine with the genes already present to form novel genetic combinations
A bacteriophage is a virus that infects its host bacterium by attaching to the bacterium, boring a hole through the bacterial cell wall, and injecting its viral DNA while its protein coat remains attached to the cell wall. Transduction occurs when fragments of the bacterial chromosome become packaged into the viral progency produced during such viral infection. These virions may infect other bacteria and introduce new genetic arrangements through recombination with the new host cell's DNA. The closer two genes are to one another on chromosome, the more likely they will be to transduce together
What's a bacteriophage?
A bacteriophage is a virus that infects its host bacterium
Inhibits spindle formation
Require presence of the substance for transcription to occur; only transcribed when needed
Inducer binds to the repressor, preventing it from binding to the operator
In a constant state of transcription, unless a co-repressor is present to inhibit; inactive repressor until it combines with the co-repressor and can only bind to the operator and prevent transcription only when it has formed repressor-corepressor complex
Co-repressor usually an end product
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