test 1 study guide

Question 1

Gene

Answer 1

DNA sequence coding for a trait

Question 2

Allele

Answer 2

version of a gene

Question 3

Locus

Answer 3

gene’s location

Question 4

Genotype

Answer 4

allele combo

Question 5

Phenotype

Answer 5

physical expression

Question 6

Segregation

Answer 6

alleles separate in gametes

Question 7

Independent assortment

Answer 7

genes on different chromosomes assort independently

Question 8

Monohybrid ratio:

Answer 8

3:1

Question 9

Dihybrid ratio

Answer 9

9:3:3:1

Question 10

Testcross

Answer 10

unknown × homozygous recessive

Question 11

Incomplete dominance

Answer 11

intermediate phenotype

Question 12

Codominance

Answer 12

both alleles expressed (AB blood)

Question 13

Penetrance

Answer 13

% of individuals showing trait

Question 14

Expressivity

Answer 14

degree of trait expression

Question 15

Lethal alleles

Answer 15

2:1 ratio

Question 16

Epistasis

Answer 16

one gene masks another (common ratios: 9:7, 9:3:4, 12:3:1)

Question 17

G1

Answer 17

growth

Question 18

S

Answer 18

DNA replication

Question 19

G2

Answer 19

prep for division

Question 20

M

Answer 20

mitosis + cytokinesis

Question 21

G0

Answer 21

non-dividing phase

Question 22

Mitosis

Answer 22

Purpose: identical cell production
No homolog pairing
One division → 2 identical diploid cells

Question 23

Meiosis

Answer 23

Purpose: gamete formation
Meiosis I: homologs separate
Meiosis II: sister chromatids separate
Crossing over occurs in prophase I
Produces 4 genetically different haploid cells

Question 24

Nondisjunction

Answer 24

Meiosis I error → homologs fail to separate
Meiosis II error → chromatids fail
Leads to aneuploidy (XO, XXY, etc.)

Question 25

XY

Answer 25

humans (male heterogametic)

Question 26

ZW

Answer 26

birds (female heterogametic)

Question 27

XO

Answer 27

insects

Question 28

Haplodiploidy

Answer 28

males = unfertilized eggs

Question 29

SRY gene

Answer 29

triggers male pathway

Question 30

Turner (XO)

Answer 30

female, sterile

Question 31

Klinefelter (XXY)

Answer 31

male, sterile

Question 32

Androgen insensitivity

Answer 32

XY but female phenotype

Question 33

Drosophila Sex Determination

Answer 33

Based on X:A ratio 1.0 → female <1.0 → male 1.0 → metafemale ~0.5 → intersex

Question 34

Autosomal Recessive

Answer 34

Skips generations Unaffected parents → affected child Equal male:female More common with consanguinity

Question 35

Autosomal Dominant

Answer 35

No skipping Affected parent → affected child Equal sexes 50% chance if heterozygous parent

Question 36

X-linked Recessive

Answer 36

Mostly males affected Carrier moms → affected sons No father → son transmission Affected fathers → all daughters carriers

Question 37

X-linked Dominant

Answer 37

Affected father → all daughters affected No sons affected from father Affected mother → 50% sons, 50% daughters

Question 38

Y-linked

Answer 38

Only males Passed father → all sons

Question 39

Linkage Basics

Answer 39

Close genes inherited together Reduce independent assortment Parental classes = most frequent Recombinants = middle frequency

Question 40

Recombination Frequency

Answer 40

RF = (recombinants ÷ total) × 100 Max RF = 50% (unlinked genes)

Question 41

Coupling vs Repulsion

Answer 41

Coupling (cis): AB / ab Repulsion (trans): Ab / aB

Question 42

Three-Point Mapping

Answer 42

Identify parentals (largest) Identify DCOs (smallest) The allele that “flips” → middle gene Map distance includes DCOs twice

Question 43

Interference

Answer 43

Interference = 1 − coefficient of coincidence If interference = 1 → no DCOs occur

Question 44

Monozygotic

Answer 44

identical genome

Question 45

Dizygotic

Answer 45

50% shared

Question 46

Concordance

Answer 46

% both twins show trait

Question 47

Amniocentesis

Answer 47

fetal cells from fluid

Question 48

CVS

Answer 48

earlier diagnosis; placental tissue

Question 49

Maternal blood screening

Answer 49

risk indicators

Question 50

Fetal cell sorting

Answer 50

fetal cells from blood

Question 51

PGD

Answer 51

embryo tested before implantation