Lecture 3

Question 1

the sex of an organism is defined by

Answer 1

• phenotype

- how it appears

Question 2

sex determination

Answer 2

the mechanism by which sex is established

Question 3

hermaphroditism

Answer 3

both sexes present in the organism

- self fertilization

Question 4

monoecious

Answer 4

bear both male and female reproductive structures

Question 5

dioecious

Answer 5

either male or female reproductive structures

Question 6

sex is determined how

Answer 6

• chromosomally
• gentically
• environmentally

Question 7

heterogametic sex

Answer 7

produces two types of gametes with respect to sex chromosomes (male in mammals is XY)

Question 8

homogametic sex

Answer 8

produces gametes that are the same in terms of sex chromosomes (female in mammals is XX)

Question 9

XX-XO

Answer 9

• females have two sex chromosomes (XX) and mammals only have one (XO).
• The O signifies no chromosome.
• The males are the heterogametic sex

Question 10

XX-XY

Answer 10

males and females have two sex chromosomes,

Question 11

ZZ-ZW

Answer 11

• the female is heterogametic (ZW) and the male is homogametic (ZZ)
• the prevent confusion between X and Y

Question 12

other types of sex determination

Answer 12

• temp of eggs for croc and turtles
• position in stack for slipper limpet
• fly determined by the balance of genes on the X and the autosomes. =1 female =.5 male >1 metafemale <1 materiel =.66 intersex

Question 13

sex determination in humans

Answer 13

the X and Y chromosomes are homologue at pseudoautosomal regions, essentially for X-Y pairing in meiosis in the male

Question 14

Turners

Answer 14

• only one x

- underdeveloped sex characteristics in the female

Question 15

Klinefelters

Answer 15

• two X and one Y

- persons are male

Question 16

X chromosome contains

Answer 16

• genetic information for both sexes

- at least one copy required for human development

Question 17

male-dermining located on

Answer 17

• Y

- a single copy results in the male phenotype

Question 18

genes for fertility on are

Answer 18

both X and Y

Question 19

SRY gene

Answer 19

• part of the Y chromosome that helps determine the individual as male.
• only a gene on the Y chromosome determines if it is a male or not. not the entire chromosome
• becomes active 6 weeks after fertilization
• causes the neutral gonads to becomes testes and secretes anti Mullein inhibiting stuff that results in the degeneration of the female organs

Question 20

the genes for male and female secondary sex characteristics are found

Answer 20

on the autosomes

Question 21

sex-linked characteristic

Answer 21

determined by genes on the sex chromosomes.

Question 22

hemizygous

Answer 22

males can’t be heterozygous or homozygous for X linked loci since they only have one X

Question 23

reciprocal cross

Answer 23

the phenotypes of males and females are reversed

Question 24

nondisjunction

Answer 24

the failure of chromosomes to separate in meiosis or mitosis

Question 25

Y linked traits

Answer 25

- present only in males. all male offspring with a Y linked trait will display it; rare - much of the Y chromosome is nonfunctional (don't code proteins) so mutations will accumulate

Question 26

palindromic sequences

Answer 26

- read the same on both strands of the DNA creating two nearly identical species - makes susceptible to deletions

Question 27

dosage compensation

Answer 27

-process that equalizes the amount of protein produced by X-linked genes in the two sexes

Question 28

fruit flies

Answer 28

genes on the X in male twice as active as those on female

Question 29

C.elegans

Answer 29

activity of both Xs in female is halved

Question 30

dosage compensation in mammals

Answer 30

- genes on one of the Xs of the female is inactivated | - females now hemizygous at X-linked locus

Question 31

Barr body

Answer 31

inactivated X chromosome that appears as a dark stained structure

Question 32

sex-influenced characteristics

Answer 32

determined by autosomal genes but expressed differently in males and females

Question 33

sex limited characteristic

Answer 33

only expressed in one sex