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Final Ib Biology Year 1-Genetics
Terms in this set (97)
A large strand of DNA usually 50-250 million base pairs long in humans. Contains many genes although only 5% or so is actually genes.
A heritable factor that consists of a length of DNA and influences a specific characteristic. Occupy a specific position on a chromosome.
One specific form of a gene differs from other alleles by one or a few bases only and occupies the same gene locus or spot on the chromosome.
Each organism can have how many alleles per gene?
2- one from mom one from dad
Genes are represented by __?
ex: B=brown hair
b= blond hair
How many alleles can a gene pool have?
Multiple- but only two are found in each individual
The two alleles you have for a trait
What is a homozygous vs heterozygous genotype?
Homo: BB or bb
What those two alleles make you look like. The characteristics of an organism
The whole of the genetic information of an organism (sum total of all possible alleles available in a particular species)
Define satellite DNA?
Most ladder steps on a chromosome are made of non-coding repetitive sequences, thought to be used for telling the genes when they should replicate and make certain proteins
Define chromosome mutation?
Occurs when there is an extra or missing chromosome. Ex: Down syndrome, turner
Define gene mutation?
Occurs when there is a change in the base sequence of a gene.
Ex: Sickle cell anemia. GAG has mutated to GTG.
A karyotype is the identification of individual chromosomes using a photograph of the DNA in a dividing cell. This can be used to identify certain genetic disorders. Arrange according to size and structure.
Chromosomes Eukaryotes vs Prokaryotes:
Prokaryotes have circular chromosomes, Eukaryotes have linear DNA. P contain plasmids, E dont. P is not associated w protein (naked DNA) and E is w histone proteins. P contains one small circular chromosome, E contains two or more chromosome types.
Who is the scientist that demonstrated that bacteria only have one circular chromosome?
What pairs do eukaryotic chromosomes form?
Homologous chromosomes. Humans have 23 pairs (one from mom, one from dad). The pairs are the same length, alleles at a gene locus.
Haploid vs Diploid definition?
Diploids have two copies of genetic material subdivided into chromosomes (46)(gametes). Haploids have one copy of genetic material subdivided into chromosomes (23) (egg/sperm).
Karyotype vs Karyogram?
Karyotype= a property of the cell- the number and type of chromosomes present in the nucleus
Karyogram= a photograph or diagram of the stained chromosomes- can diagnose chromosomal abnormalities
Autosomes vs Sex Chromosomes?
Autosomes are all the chromosomes that do not deal with gender. Sex chromosomes are the chromosomes that determine gender.
Karyograms during divisions look like what?
Sister chromatids of duplicated chromosomes are there. Two on each.
Define theoretical genetics?
Concerned with the probabilities associated with producing offspring of a particular genotype or phenotype.
Who is Gregor Mendel?
Father of genetics who used thousands of pea plants, called the inherited particles factors
Define dominant allele?
An allele that has the same effect on the phenotype whether it is present in the homozygous or heterozygous state. Ex: Bb and BB give you brown hair.
Define recessive allele?
An allele that only has an effect on the phenotype when present in the homozygous state.
Define codominant alleles?
Pairs of alleles that both affect the phenotype when present in a heterozygote. Ex: CRCW = pink flower, because both red and white gene are codominant.
The particular position on homologous chromosomes of a gene.
An individual that has a recessive allele of a gene that does not have an effect on their phenotype.
What are the steps for working out a punnett square problem?
1. choose a letter to represent the gene. Choose one that has a distinctly different upper and lower case
2. Represent the genotype of each parent with a pair of letters- place one parent on the top of the grid and the other parent on side of the grid.
3. combine pairs of letters to represent the possible genotypes of the offspring
4. From genotypes work out the possible phenotypes of the offspring.
What do you do if you have an unknown parent?
Test cross- testing a suspected heterzygote by crossing it with a known homozygous recessive
What is the difference between the X and Y chromosome?
X is larger and carries more genes. Ex: colorblindness, hemophilia.
What is an example of a gene located only on the y chromosome?
Define sex linkage?
Genes that are carried on the sex chromosomes, almost always on the "X"
What does hemophilia look like?
Define pedigree chart?
Used to show the inheritance of traits over several generations.
Blood type is an example of what?
Codominance and multiple alleles. AB
Name some genetic diseases?
.Cystic Fibrosis (CF)
Autosomal recessive trait
Found on Chromosome 7
Autosomal Recessive trait- reduces production of hemoglobin
Found on chromosome 11
Prevalent in countries where malaria is endemic
Affects gene that codes for the beta chain of hemoglobin
Autosomal dominant mutation- increases the length of a repeated sequence CAG
Progressive breakdown of nerve cells in the brain- muscle coordination
Found on chromosome 4
What are mutation rates?
Spontaneous permanent changes in the base sequence of DNA. The natural rate is slow but environmental factors can increase.
What are mutagens?
Factors that increase the mutation rate (UV light, Mutagenic chemicals, Radiation)
What are the types of gene mutation?
Substitution, insertion, deletion, inversion
What is the goal of meiosis?
To make gametes, also known as sex cells.
What are the diploid and haploid number?
Diploid is when there are two sets of each chromosome present, haploid is one set.
One diploid cell makes how many haploid cells? Through what process?
4 haploid cells by reduction division
What are homologous chromosomes?
Pairs of two sister chromatids from (either the maternal or paternal).
What is meiosis?
They process by which reduction from a diploid cell to a haploid cell occurs.
What are the two steps of meiosis and what do they each consist of?
Interphase, Prophase I, Metaphase I, Anaphase I, Telophase I
Same but no interphase and everything II
What occurs during prophase 1?
-Supercoiling of chromosomes
-Synapsis: pairing of homologous chromosomes into a bivalent/tetrad
-Spindle microtubules form and nuclear envelope breaks down
What is crossing over?
The exchange of DNA between non-sister homologous chromatids. Happens during Prophase 1.
What are recombinants?
The resulting chromosomes from crossing over are called recombinants.
What are the results of crossing over?
Produces a new combination of alleles.
What happens during metaphase I?
Bivalents line up on equator, orientation is random on where the maternal and paternal chromosomes line up. Centromere attached to spindle microtubules.
What happens during anaphase I?
Pairs of homologous chromosomes split, centromeres do not split. Homologous chromosomes separate?
What happens during telophase I?
Chromosomes arrive at poles, spindles disappear, chromosomes uncoil. Reduction of chromosomes number from diploid to haploid is complete.
What happens during prophase II and metaphase II is the same just with two cells with haploid.
What happens during Anaphase II?
Chromosomes separate and move towards opposite poles.
Centromere does split.
Sister chromatids separate.
What happens during Telophase II?
Spindle disappears, nuclear membrane reforms. Chromosomes into chromatin.
What are the end results of meiosis?
4 sperm or 1 egg and 3 polar bodies.
What is non-disjunction?
Centromeres don't uncouple leading to an extra or missing chromosome. Ex: Downs syndrome
What is karyotyping?
-Done to check for non-disjunction or other
-Performed using cells collected by chronic villus
sampling OR amniocentesis
-Karyotyping is arranging the chromosomes in
pairs according to their size and structure
-Testing for chromosomal abnormalities
How does meiosis create species variety?
Through random alignment in metaphase I. Also crossing over. Also fertilization combines maternal and paternal alleles.
What is the Law of Independent Assortment?
Homologous chromosomes separate independently of other homologous chromosomes, allowing for many combinations in gametes, and ultimately, in the zygote that is formed by egg and sperm.
What is Mendel's Law of Segregation?
During meiosis, the separation of a pair of parental factors occurs in such that only one factor is present in each gametes.
What does aneuploidy mean?
One chromosome missing or one extra chromosome (resulting from non-disjunction).
Cell has 3n number. (All homologs move to one gamete- happens in plants).
What are linked genes?
Genes whose locus are relatively close to each other, and are therefore less likely to be separated by crossing over.
What do dihybrid crosses involve?
Unlinked autosomal genes.
What is a linkage group?
A group of genes whose loci are on the same chromosome.
What are recombinants?
Offspring in which the genetic information has been rearranged by crossing over so as to produce phenotypes that are different than those of the parents.
What is variation?
The differences that exist between individuals.
What are the two types of variation?
Discrete or discontinuos
-Clearly distinguishable, not controlled by environmental factors, blood groups and left handedness
-Controlled by environmental factors
-Height, crops yield
What is polygenic inheritance?
Occurs when a phenotype is controlled by more than one gene, resulting in a mosaic of phenotypes.
What are genetic engineering procedures?
-PCR and Gel Electrtophoresis
What does PCR stand for?
Polymerase chain reaction
What does PCR do?
Copies and amplifies minute quantities of nucleic acid. Driven by heating and cooling cycles. Uses synthetic primers, targeted to start before gene of interest.
What are some applications of PCR?
-40,000 year old wooly mammoth
-Minute blood samples from crime scene
-DNA from embryonic cells to genetic screening
What is gel electrophoresis?
Separating DNA according to their charge and size to identify natural variations found in every individuals DNA. DNA is slightly negative so it moves towards positive ends of gel.
What are restriction enzymes?
Used to cut DNA into fragments at very precise points. Produces "sticky ends"
What are some applications of Gel Electrophoresis?
Family relationships for immigrants
Determine if rare birds and other animals are being sold as captive bred or actually stolen
What is genetic modification?
The transfer of genes from one species to another
-Has been carried out for 1000s of years
Gene transfer between species is....
Possible because the DNA code is universal. The same RNA codon codes for the same amino acids in a mRNA strand.
How are genes transferred?
1. Insertion of gene into plasmid using restriction enzyme and DNA ligase
2. Introduction into plant cells in culture
3. Regeneration of plant
What is needed for bacterial transformation?
-A gene we want to transfer
-Two enzymes (ligase and restriction enzyme)
What do you do for gene cloning with bacterial transformation?
Cut out gene of
Cut vector (plasmid)
with same restriction
Insert gene into
plasmid and ligate
Induce bacterium to
take up recombinant
What are GMOS?
Genetically modified organisms, also known as transgenic organisms.
What are two examples of GMOs?
A gene from a bacteria was added so
that the plant would produce a toxin that
makes them resistant to insects
Genes from daffodils and bacteria were
added to add vitamin A to the rice (Vit A
defiency in countries where a lot of rice
was eaten was cause blindness and
Give an example of a genetically modified animal?
Bacteria produce a growth hormone in cattle. 10-20% more milk.
What are the benefits of BT corn?
Damage to crop by the
European corn borer (ECB) is
Bt corn is slightly more
expensive but is cheaper than
applying the insecticide
Non-Bt corn needs checking
for sign of ECB- Bt corn does
Less insecticide means less
impact on environment and
lower health risk for workers
What are the harmful effects of BT corn?
Also kills other insects
Insects may develop
resistance to Bt toxin
Resistant insects make the
Bt spray useless
Difficult to prevent the pollen
of Bt corn from traveling to a
field of non-Bt corn which is
then no longer organic
Could spread to wild species
Human food crops could
become controlled by a
small number of biotech
What is a clone?
A group of genetically identical organisms or a group of cells artificially derived from a single parent cell. Ex: The sheep dolly.
What are some cloning techniques?
Farm animals- take 8 cell embryo cluster of undifferentiated cells.
Separate, and implant in 8 different mothers.
Dolly the sheep- take DNA from one cell and inject into nucleus of
another cell (it's own DNA removed). Zap with electricity to start
What is the purpose of therapeutic human cloning?
To create embryo to supply stem cells for medical use. Same format as reproductive cloning but when the cell is a blastocyst the ball is broken open and stem cells are cultured.
What are the good ethics of therapeutic human cloning?
Cells grown are genetically identical to the adult so there are no
difficulties with rejection and no need for anti-rejection drugs
Stem cells can develop into any type of cell
Potential to repair damage or failure caused by injury or disease
Further potential- they could become a complete organ
What are the bad ethics of therapeutic human cloning?
Requires formation of an embryo that is then destroyed
If embryo was not destroyed = a clone of the individual
More research needed on adult stem cells
Stem cells can develop into tumor cells
What are some examples of gene therapy?
Cystic fibrosis- disfunction of lungs and other
SCID (immune deficiency), replaced gene allows
for the production of the enzyme ADA
(adenosome deaminase), which helps person
fight off infection.
Cure for thalassemia- blood disorder, inability to
make proper hemoglobin. Result, anemia. Cure
is in sight
What is genetic screening?
Testing an individual for the presence of absence of a gene.
What are the good ethics of genetic screening?
What are the bad ethics of genetic screening?
Invasion of privacy
associated with having a
Abort of fetus if problems
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