Genetics

Question 1

Genes

Answer 1

DNA sequences that code for heritable traits

Question 2

Alternative forms of genes = ______

Answer 2

Alleles

Question 3

Locus

Answer 3

Location of gene on a specific chromosome

Question 4

Hemizygous

Answer 4

Only one allele is present for a given gene

• Ex. X chromosome in males

Question 5

Codominance

Answer 5

More than one dominant allele for a gene

Question 6

Incomplete dominance

Answer 6

Heterozygote expresses intermediate phenotype b/w two homozygous genotypes

• Red + white flowers = pink

Question 7

Penetrance

Answer 7

Probability someone will express a phenotype given a certain genotype

Question 8

Expressivity

Answer 8

Varying phenotypes having the same genotypes

Question 9

Mendel’s First Law (segregation)

Answer 9

Separating homologous chromosomes is done during anaphase I of meiosis I => each gamete carries only one allele for a given trait

Question 10

Mendel’s Second Law (independent assortment)

Answer 10

Inheritance of one gene does not affect inheritance of another

• Some genes are linked
• Prophase I of meiosis

Question 11

Transposons

Answer 11

Can insert and remove themselves from gene pool

Question 12

Missense mutation

Answer 12

Change in nucleotide => substitute one amino acid for another in final protein

Question 13

Nonsense mutation

Answer 13

Change in nucleotide => substitutes stop codon for an AA in final protein

Question 14

Inversion mutation

Answer 14

Segment of DNA is reversed in chromosome

Question 15

Translocation mutation

Answer 15

Segment of DNA from one chromosome is swapped with segment of DNA from another chromosome

Question 16

Inborn errors of metabolism

Answer 16

Defects in genes required for metabolism

Question 17

Genetic leakage

Answer 17

Flow of genes b/w species

Question 18

Genetic drift

Answer 18

Changes in composition of gene pool due to chance

Question 19

Founder effect

Answer 19

Small population is isolated from other populations due to natural barriers/catastrophic events

Question 20

Bottlenecks

Answer 20

Drastically reduce size of population available for breeding

Question 21

Inbreeding

Answer 21

Encourages homozygosity

Question 22

Inbreeding depression

Answer 22

Loss of genetic diversity => reduced fitness

Question 23

Test cross

Answer 23

Determines an unknown genotype => crossed w/ homozygous recessive

Question 24

Dihybrid cross

Answer 24

Cross 2 heterozygotes => 9:3:3:1

• 3:1 phenotypic ratio still holds (Mendel’s 2nd Law)

Question 25

Sex-linked

Answer 25

X-linked - Diseases are more common in males

Question 26

Chiasma

Answer 26

Point of crossing over - More likely for genes that are further apart

Question 27

Hardy-Weinberg criteria

Answer 27

- No genetic drift - No mutations - Random mating - No migration - No differential reproductive success

Question 28

Hardy-Weinberg equations

Answer 28

(p + q)^2 = 1 - Frequency of alleles p^2 + 2pq + q^2 = 1 - Frequency of phenotypes

Question 29

Differential reproduction

Answer 29

Mutation/recombination => gene that is favorable => more likely to pass it on to next generation (and vice versa)

Question 30

Stabilizing selection

Answer 30

Keeps phenotypes w/in a certain range by selecting against extremes

Question 31

Directional selection

Answer 31

Select for what was initially an extreme

Question 32

Disruptive selection

Answer 32

Two extremes are selected for over what was initially the norm

Question 33

Prezygotic mechanisms

Answer 33

Different species try to breed => formation of zygote is prevented

Question 34

Postzygotic mechanisms

Answer 34

Different species try to breed => nonviable/sterile offspring

Question 35

Aneuploidy

Answer 35

Having one or more extra/missing chromosomes - Usually results from nondisjunction during meiosis

Question 36

Heterochromatin

Answer 36

Genes that are not currently being transcribed - Prone to higher levels of DNA methylation than euchromatin

Question 37

Euchromatin

Answer 37

Chromatin being actively transcribed

Question 38

Prophase

Answer 38

Membrane begins to disintegrate and chromosomes condense - Meiosis I: tetrad formation, genetic recombination, spindle apparatus formation

Question 39

What stage of cell cycle does replication occur during?

Answer 39

S phase (which is a part of interphase)

Question 40

Anaphase

Answer 40

Chromosomal migration

Question 41

How are meiosis II and mitosis similar?

Answer 41

Ploidy is maintained (number of chromosomes does not change)

Question 42

Nondisjunction

Answer 42

A parent provides too many/doesn't provide enough chromosomes

Question 43

Primary spermatocyte + how many chromosomes/chromatids it has

Answer 43

Primary spermatocyte = spermatogonium just after DNA replication - 46 chromosomes (humans never have more than that) - 92 chromatids