MCAT: Genetics
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89 Terms
What is a phenotype?
The observable traits of an organism.
What is a genotype?
The genetic makeup of an organism.
What is a gene?
A stretch of DNA that codes for a trait or protein.
What is a locus?
The location of a gene on a chromosome.
What is an allele?
A variant form of a gene.
How many alleles of a gene does a diploid cell carry?
two
Where are alleles of the same gene found?
At the same locus on homologous chromosomes.
What are the ABO blood type alleles?
IA, IB, and i.
What genotype produces blood type AB?
IAIB.
What genotype produces blood type O?
ii.
What does homozygous mean?
Having two identical alleles.
What does heterozygous mean?
Having two different alleles.
What is the wild-type allele?
The most common or “normal” allele in a population.
What is complete dominance?
The dominant allele completely masks the recessive allele.
In complete dominance, what phenotype does Aa show?
Dominant phenotype.
What is codominance?
Both alleles are fully expressed.
What is an example of codominance?
AB blood type.
What is incomplete dominance?
Heterozygotes show an intermediate phenotype.
What is an example of incomplete dominance?
Blue-gray chickens from black × white chickens.
What is penetrance?
The percentage of individuals with a genotype who express the phenotype.
What is expressivity?
The degree to which a trait is expressed.
What is variable expressivity?
Individuals show different severities of the same trait.
What is hybrid vigor?
Increased viability from genetically diverse parents.
Why does hybrid vigor occur?
Lower chance of inheriting harmful recessive alleles.
What is a gene pool?
All alleles in a population.
What is the main purpose of meiosis?
Generate genetic diversity and produce haploid gametes.
What two mechanisms generate genetic recombination?
Independent assortment and crossing over.
How many divisions occur in mitosis?
one
How many divisions occur in meiosis?
Two.
What is the ploidy of mitotic daughter cells?
Diploid (2n).
What is the ploidy of meiotic daughter cells?
Haploid (n).
Are daughter cells identical in mitosis?
Yes.
Are daughter cells identical in meiosis?
No.
What is independent assortment?
Random distribution of homologous chromosomes into gametes.
During which stage does independent assortment occur?
Metaphase I of meiosis.
How does independent assortment increase diversity?
Creates new chromosome combinations in gametes.
What are linked genes?
Genes located on the same chromosome.
How does crossing over affect linkage?
Reduces linkage by exchanging DNA.
Are genes farther apart or closer together more likely to recombine?
Farther apart.
What is recombination?
Formation of new allele combinations during meiosis.
During which phase does crossing over occur?
Prophase I.
What is the chiasma?
The physical site of crossing over.
What is synapsis?
Pairing of homologous chromosomes.
What is a tetrad?
Paired homologous chromosomes during meiosis.
What is the synaptonemal complex?
Protein structure holding homologous chromosomes together.
How many recombinant chromatids result from a single crossover?
2 out of 4.
What are sx-linked traits?
Traits determined by genes on sx chromosomes.
Which chromosome carries most sx-linked genes?
X chromosome.
Why are Y-linked traits rare?
The Y chromosome carries few genes.
What chromosome combination determines females?
XX.
What chromosome combination determines males?
XY
What is cytoplasmic inheritance?
Inheritance of organelle DNA outside the nucleus.
Which parent contributes mitochondria to offspring?
The mother.
What is a mutation?
A change in DNA sequence not caused by recombination.
What is a base substitution mutation?
One nucleotide is replaced by another.
What is an inversion mutation?
DNA segment reattaches in reverse orientation.
What is an insertion mutation?
Addition of nucleotides into DNA.
What is a deletion mutation?
Removal of nucleotides from DNA.
What type of mutation do insertions and deletions often cause?
Frameshift mutations.
What is a translocation mutation?
DNA segment moves to another location.
What is mispairing?
Incorrect base pairing during replication.
What is an advantageous mutation?
A mutation that improves fitness.
What is a deleterious mutation?
A mutation that harms fitness.
What is an inborn error of metabolism?
Genetic disease causing metabolic dysfunction.
What is PKU?
Phenylketonuria; inability to metabolize phenylalanine.
What is a mutagen?
Something that causes mutations.
What is a carcinogen?
A mutagen that causes cancer.
Are all mutagens carcinogens?
No
are all carcinogens mutagens?
Yes.
What is genetic drift?
Random changes in allele frequencies due to chance.
What is the Hardy-Weinberg equation for allele frequencies?
p+q=1
What is the Hardy-Weinberg equation for genotype frequencies?
p2+2pq+q2=1
What does p represent in Hardy-Weinberg equations?
Frequency of the dominant allele.
What does q represent in Hardy-Weinberg equations?
Frequency of the recessive allele.
What are the five assumptions of Hardy-Weinberg equilibrium?
No mutation, no migration, no natural selection, random mating, and infinitely large population.
What is a test cross?
Crossing an unknown dominant genotype with a homozygous recessive.
What is a back cross?
Crossing offspring with a parent.
What is the parental (P) generation?
The original parents.
what is the F1 generation?
The offspring of the parental generation.
What is the F2 generation?
Offspring of the F1 generation.
What is gene mapping?
Determining physical locations of genes on chromosomes.
What does a higher crossover frequency indicate?
Genes are farther apart.
What is biometry?
Statistical analysis of biological data.
What is the null hypothesis?
Assumption that no relationship exists in the data.
What does p < 0.05 mean?
less than 5% chance results occurred randomly.
What statistical test compares two groups?
t-test.
What does variance measure?
Spread of data.
What does standard deviation measure?
Dispersion around the mean.
What is skew?
Asymmetry of a distribution curve.