test 1

Question 1

Principle of Segregation?

Answer 1

Alleles separate in meiosis; each gamete gets one.

Question 2

Independent Assortment?

Answer 2

Genes on different chromosomes assort independently.

Question 3

Testcross purpose?

Answer 3

Determine unknown genotype by crossing with homozygous recessive.

Question 4

9:3:3:1 ratio comes from what?

Answer 4

Dihybrid cross with independent assortment.

Question 5

Genotype vs phenotype?

Answer 5

Genotype = alleles
phenotype = expressed trait.

Question 6

Incomplete dominance?

Answer 6

Heterozygote shows intermediate phenotype.

Question 7

Codominance

Answer 7

Both alleles expressed equally (e.g., AB blood).

Question 8

Epistasis

Answer 8

One gene masks another gene’s expression.

Question 9

Lethal allele ratio?

Answer 9

2:1 in surviving offspring.

Question 10

Universal donor/recipient?

Answer 10

O = donor; AB = recipient.

Question 11

SRY gene function?

Answer 11

Initiates male development.

Question 12

Why X-linked recessive common in males?

Answer 12

Males have only one X (hemizygous).

Question 13

Can fathers pass X-linked traits to sons?

Answer 13

No — sons get Y from father.

Question 14

X-inactivation?

Answer 14

One X chromosome is silenced in females.

Question 15

Autosomal recessive pattern?

Answer 15

Skips generations; unaffected parents → affected kids; consanguinity common.

Question 16

Autosomal dominant pattern?

Answer 16

Appears every generation; affected parent → affected child.

Question 17

X-linked recessive pattern?

Answer 17

Mostly males; carrier mothers → affected sons; no father → son transmission.

Question 18

X-linked dominant pattern?

Answer 18

Affected fathers → all daughters; no sons.

Question 19

Y-linked pattern?

Answer 19

Only males; passed father → all sons.

Question 20

Linkage

Answer 20

Genes close together on same chromosome; inherited together.

Question 21

What creates recombinants?

Answer 21

Crossing over in meiosis I.

Question 22

Recombination frequency formula?

Answer 22

(Recombinants ÷ Total) × 100.

Question 23

Max recombination frequency?

Answer 23

50% = genes unlinked.

Question 24

Parental classes?

Answer 24

Two largest groups in testcross.

Question 25

Double crossovers?

Answer 25

Two smallest groups.

Question 26

Determining gene order?

Answer 26

Compare parentals to DCOs; the allele that flips = middle gene.

Question 27

Interference?

Answer 27

1 − coefficient of coincidence.

Question 28

Genes come in different versions called?

Answer 28

Alleles

Question 29

Best model organism (short generation time + many offspring)?

Answer 29

Yeast, Arabidopsis, Drosophila, C. elegans (NOT humans).

Question 30

Why was early 1900s important for genetics?

Answer 30

Rediscovery of Mendel + Morgan’s fruit fly mutants.

Question 31

Which is NOT part of eukaryotic cell cycle?

Answer 31

G0 is not part of the dividing cycle

Question 32

When does DNA replication occur?

Answer 32

S phase

Question 33

What is true about sperm?

Answer 33

Sperm may contain X or Y; determine sex.

Question 34

If females are heterogametic, males homogametic, what is example?

Answer 34

Female AB, Male BB (female produces two gametes).

Question 35

Haplodiploidy?

Answer 35

Males from unfertilized eggs females from fertilized.

Question 36

Sex phenotype of XXXY Drosophila?

Answer 36

Metafemale (extra X → female).

Question 37

Calvin Bridges’ unexpected sex-linked results explained by?

Answer 37

Nondisjunction

Question 38

Bearded dragon sex determination?

Answer 38

Chromosomes + temperature.

Question 39

XO humans (one X only) is called?

Answer 39

Turner syndrome.

Question 40

Key differences between mitosis and meiosis?

Answer 40

Pairing of homologs, 2 divisions in meiosis, genetically different gametes.

Question 41

False statement: "Sister chromatids separate during mitosis but NOT meiosis."

Answer 41

Incorrect — they separate in meiosis II.

Question 42

Incomplete dominance?

Answer 42

Heterozygote shows intermediate phenotype.

Question 43

Creeper chickens (dominant lethal): ratio from two creepers?

Answer 43

2 creeper : 1 normal.

Question 44

9:7 epistasis ratio — what genotype is in the “9”?

Answer 44

A_B_ (any genotype with at least one dominant allele at both genes).

Question 45

Least appropriate genetic model organism?

Answer 45

Humans (long generation time + few offspring).

Question 46

Segregation?

Answer 46

Alleles separate during gamete formation.

Question 47

What phase replicates DNA?

Answer 47

S-phase.

Question 48

Which is NOT part of the cell cycle?

Answer 48

G0

Question 49

Homologs pair in which division?

Answer 49

Meiosis I only.

Question 50

Human XY system

Answer 50

Male = XY Female = XX SRY gene = male development

Question 51

ZW system

Answer 51

Birds, butterflies Female = ZW (heterogametic) Male = ZZ

Question 52

Haplodiploidy

Answer 52

Bees/ants Female = fertilized diploid Male = unfertilized haploid

Question 53

Environmental (temperature)

Answer 53

Many reptiles Example: bearded dragons (both chromosomal + temperature)

Question 54

What system uses fertilized vs unfertilized eggs?

Answer 54

Haplodiploidy

Question 55

Drosophila sex determination:

Answer 55

Sex depends on X:A ratio Extra X → metafemale X0 → male but sterile

Question 56

Nondisjunction

Answer 56

Improper separation of chromosomes Calvin Bridges explained unexpected phenotypes from nondisjunction

Question 57

XXXY Drosophila phenotype?

Answer 57

Metafemale

Question 58

Bridges’ unexpected white/red-eye results explained by?

Answer 58

Nondisjunction

Question 59

Human Sex-Linked Disorders

Answer 59

Turner syndrome = XO Klinefelter = XXY Androgen insensitivity = XY but female phenotype

Question 60

Incomplete dominance

Answer 60

Intermediate phenotype Example: red x white → pink

Question 61

Codominance

Answer 61

Both alleles expressed

Question 62

Lethal alleles

Answer 62

2:1 surviving ratio

Question 63

Epistasis

Answer 63

One gene masks the phenotype of another 9:7 = complementary gene action 9:3:4, 12:3:1, etc. (only basics usually tested)

Question 64

Cross two creepers (dominant lethal). Ratio?

Answer 64

2creeper : 1 normal.

Question 65

9:7 ratio represents?

Answer 65

Complementary epistasis (need at least one dominant allele at BOTH genes).