Genetics Exam I

no math, only terms

centromere

site of kinetochore and microtubule binding

synapsis

close approach and contact between homologous chromosomes during P1

chiasma

points of contact/crossing over between homologous chromosome

kinetochore

connects spindle fiber to centromere

G1

gene expression, prep for DNA synthesis

S

DNA replication and chromosome duplication

G2

prep for cell division

M

cell division, mitosis/meiosis

What is the point of crossing over, independent assortment, and random assortment?

Crossing over creates new allele combinations by swapping phyiscal segments between homologous chromosomes, while independent assortment randomly distributes these into gametes. Random assortment ensures that any sperm can fuse with any egg

If there is a duplication of the same allele, is it M2 or M1

M2

If there is a duplication on different chromosomes, is it M2 or M1?

M1

Where does nondisjunction occur in anaphase I?

homologous chromosomes

Where does nondisjunction occur in anaphase/anaphase II?

sister chromatids

aneuploidy

gain/loss of a single chromosome (monosomy and trisomy)

Why is aneuploidy usually lethal?

it disrupts gene dosage

euploidy

gain/loss of a full set of chromosomes (diploidy and polyploidy)

autopolyploidy

addition of sets of chromosomes, diploid gamete is produced from 2 sperm in 1 ovum

allopolyploidy

combination of chromosome sets from different species; haploid gametes fuse then go through mitosis

locus

fixed position of a gene on a chromosome

product rule

AND (one exact outcome, no coefficient)

sum rule

OR (order doesn’t matter, coefficient)

wild type allele

most common, normal version of a gene

loss of function mutation

reduces or eliminates normal function

gain of function mutation

new or increased activity

null mutation

loss of function mutation that eliminates the function of the gene entirely

complete dominance

one allele completely masks the other

incomplete dominance

blended phenotype, 1:2:1 (red: pink: white)

codominance

both allele’s fully expressed (ABO blood type)

recessive lethal allele

causes death when homo recessive (2:1)

dominant lethal allele

cause death when min. 1 copy is present (0:1)

autosomal dominant

non sex chromosome; in all generations

autosomal recessive

on non sex chromosome; skips generations

dihybrid cross

Aa x Aa (9:3:3:1)

recessive epistasis

homozygous recessive trait masks the other traits (9:3:4)

dominant epistasis

homozygous dominant allele masks another gene (12:3:1)

testcross

Aa x aa (1:1)

true breeding cross

AA x aa, fully dominant (1:0)

complimentary gene interaction

2 dominant alleles are required for phenotype (9:7)

in pedigrees, what shape is a female?

circle

in pedigrees, what shape is a male?

square

dosage compensation

random x inactivation so that there is equal gene expresion between XY and XX, where one X chromosome is randomly inactivated in each cell

complementation

test to see if two mutations that cause same phenotype are in the same or different gene

If offspring are mutant, what does that mean for complementation?

the mutation is on the same gene, so there is no complementation

If offspring are normal, what does that mean for complementation?

it is on a different gene, so complementation occurred

What is the null hypothesis for Harvey-Weinberg X² problems?

There is no significant difference between the observed and expected, so the population is in Harvey-Weinberg equilibrium.

What is the smallest unit of evolution?

population

founder effect

small group starts new population

bottleneck

population drastically reduces

directional selection

favors one extreme phenotype

stabilizing selection

favors intermediate phenotype

disruptive

favors both extremes over middle

Hardy-Weinberg equilibrium

1. no mutation

2. no gene flow

3. no genetic drift

4. no natural selection

5. random mating