Chapter 3

Question 1

allele

Answer 1

one or two alternative forms of a gene

Question 1

What is a gene

Answer 1

inherited factor that determines a characteristic

Question 2

locus

Answer 2

specific place on a chromosome, occupied by an allele

Question 3

Conclusions made about Mendel’s experiment?

Answer 3

-inherit genetic factors from both parents
- both alleles in plants separate when gametes are formed (both from each parent)
- concept of dominance - dominant allele shown in F1 progeny and recessive allele disappeared
- two alleles separate from an individual plant with equal probability

Question 4

Principle of segregation:

Answer 4

each diploid organism has two alleles for a specific characteristic , one from each parent and these two alleles separate when gametes are formed

Question 5

Principle of dominance

Answer 5

when two different alleles are present in a genotype, only the trait encoded by one of them (the dominant allele) will be shown

Question 6

Binomial Expansion

Answer 6

(p+q)^n → p is the probability of one event, q equals the probability of the alternative event, and n equals the number of times the event occurs

Question 7

Testcross

Answer 7

individual of unknown genotype is crossed with another individual with a homozygous recessive genotype for the trait in question

Question 8

Principle of Independent assortment:

Answer 8

alleles at different loci separate independently of one another

Question 9

when do genes assort independently?

Answer 9

in anaphase I of meiosis

Question 10

Sex linked characteristics:

Answer 10

characteristics determined by genes located on the sex chromosomes

Question 11

What did Morgan Find with Drosophila

Answer 11

• found that eye color is X-linked trait and present on the X chromosome
• females can be homozygous or heterozygous for the eye-color trait because they have two X chromosomes; however, males only have one X chromosome, thus they only carry one eye-colored allele

Question 12

Nondisjunction

Answer 12

two chromosomes fail to separate in anaphase I of meiosis; 1/2 of the eggs receive two copies of the X chromosome and the other half receive only 1 copy of a Y chromosome

Question 13

sex-determination

Answer 13

mechanism by which biological sex is established

Question 14

hermaphroditism

Answer 14

both sexes are present in the same organism

Question 15

monoecious

Answer 15

an organism that has both male and female reproductive organs

Question 16

Dioecious:

Answer 16

species in which an individual organism has male or female reproductive structures

Question 17

XX-XO Sex determination

Answer 17

Females have XX and Males have XO,
In meiosis in females, the two X chromosomes pair and then separate and the one X chromosome enters each haploid egg

Question 18

XX-XY sex determination

Answer 18

-Females have XX and males have XY
-Y Chromosome is acrocentric
- Female is homogametic
-The X and Y chromosomes are only homologous at the pseudoautosomal regions

Question 19

ZZ-ZW sex determination

Answer 19

• Female is heterogametic and male is homogametic
• Females have ZW and males have ZZ chromosomes
• FOUND IN BIRDS, reptiles, butterflies, amphibians, and fishes

Question 20

what gene determines the male phenotype in mammals?

Answer 20

SRY gene on Y chromosome

Question 21

Sequential hermaphroditism:

Answer 21

each individual animal can be both male and female although not at the same time

Question 22

Turner syndrome:

Answer 22

are female and have underdeveloped secondary sex characteristics, have a single X chromosome

Question 23

Klinefelter syndrome

Answer 23

have cells with one or more Y chromosomes and multiple X chromosomes

Question 24

Poly-X females:

Answer 24

possess three X chromosomes

Question 25

role of sex chromosomes