Lec 11-1

Question 1

Two processes of sexual reproduction

Answer 1

Meiosis and fertilization

Cycle between the two leads to alternation of haploid and diploid cells

Question 2

Most organisms have

Answer 2

Two sexes

Question 3

Biological sex

Answer 3

Sexual phenotypes

Question 4

Males produce

Answer 4

Small gametes

Question 5

Females produce

Answer 5

Large gametes

Question 6

Gender

Answer 6

Category assigned by the individual (identity) or other based on behavioral and cultural practices

Question 7

Monoecious Hermaphroditism

Answer 7

Male and female at the same time

Question 8

Diocious

Answer 8

Male or female

Question 9

Sex determination

Answer 9

Biological mechanisms that regulate sexual phenotypes

Remarkably, the mechanisms of sex determination varies wildly across different organisms

Question 10

Sex determination methods

Answer 10

Chromosomally

Genetically

Environmentally

Question 11

Chromosomal sex determining systems

Answer 11

Sex is determined by the presence of a few sex chromosomes

Autosomes (non-sex chromosomes) vs sex chromosomes

Question 12

Most XX-XY species

Answer 12

Female is XX male is XY

Question 13

Y chromosome

Answer 13

Y shaped and acrocentric- one chromosome arm is much shorter than the other

Question 14

XX-XY system

Answer 14

Like homologous autosomes

Sex chromosomes pair during metaphase and segregate independently

Question 15

Sex chromosomes and autosomes pair because

Answer 15

They are homologous in small regions called pseudo autosomal regions

Question 16

Crossing a male and a female from the XX-XY system produces a

Answer 16

1:1 male and female progeny

Question 17

Males are the

Answer 17

Heterogametic sex

Question 18

Females are

Answer 18

The homogametic sex

Question 19

XX-XO system

Answer 19

System found in grasshoppers and is simplest sex determination system

Females- XX

Males- X(O)

O indicates lack of sex chromosome

Question 20

XX-XO generates

Answer 20

1:1 ratio in sex

Question 21

ZZ-ZW system

Answer 21

Found in bearded dragons and birds

Females- heterogametic
Males- Homogametic

Z and W are used to prevent confusion

Question 22

Sex in the chromosomal sex-determining systems is determined by

Answer 22

Individual genes located on sex chromosomes working in conjunction with genes on autosomes

Question 23

Genic sex determination

Answer 23

Some organisms have no obvious differences in the chromosomes between males and females

These organisms have genic sex determination

Genotypes at one or more loci determine the sex of an individual without specific sex chromosomes

Question 24

Environmental sex determination

Answer 24

Number of organisms determine sex based on environmental factors

Question 25

Marine mollusks

Answer 25

First mollusks to attach to a free substrate are female A new male mollusk is attracted to chemicals released by female they mate Overtime the male mollusk becomes female Another male is attracted to this female and the process repeats

Question 26

Sequential hermaphroditism

Answer 26

Each individual can be both male and female but not at the same time

Question 27

Temperature can determine sex during

Answer 27

Embryonic development in many turtles, crocodiles and alligators Other animals like bearded dragons use sex chromosomes but temperature can override this

Question 28

Calvin Bridges XX-XY system

Answer 28

Proposed that in fruit flies sex was determined not by the amount of X and Y chromosomes but instead the balance between female determining genes on X male-determining genes on the autosomes

Question 29

Bridges proposed that fly sex is determined by

Answer 29

X:A ratio (number of X chromosomes divided by number of haploid sets of autosomes)

Question 30

Normal flies have 2 haploid sets of autosomes and 2X for females and 1X for males, so

Answer 30

Normal male X:A = 1/2 = .5 Normal female X:A = 2/2 = 1

Question 31

Autosome numbers indirectly affect

Answer 31

developmental timing and X linked gene expression.

Question 32

XX-XY system humans

Answer 32

Drosophila and humans share XX-XY However, unlike drosophila the y chromosome determines sex in humans Male determining region is mapped on the Y chromosome

Question 33

SRY

Answer 33

Sex determining Region Y gene Genetic engineering in mice placed just the SRY gene in XX mice and these mice were anatomically male

Question 34

Role of sex chromosomes in humans

Answer 34

X chromosome contains genes essential for both sexes Male-determining gene on the Y (even if extra X chromosomes, if there is a Y they are likely a male) Absence of Y leads to female sex Fertility genes located on X and Y Additional X chromosomes can upset normal development of males or females

Question 35

Turner Syndrome

Answer 35

Genotype- XO Female with underdeveloped secondary sex characteristics

Question 36

Klinefelter syndrome

Answer 36

XXY or XXXY Men with small testis, reduce facial and pubic hair, sterile, tall Normal intelligence

Question 37

Poly-X females

Answer 37

Triple-X syndrome XXX No distinctive features other than tendency to be tall/thin Intellectually disability risk is increased Some have 4 or 5 Xs and intellectual and physical disabilities

Question 38

Androgen-insensitivity syndrome

Answer 38

Normal male chromosome (XY) But Female external sexual characteristics but fail to menstruate. Vagina but no uterus, oviducts, or ovaries. Inside abdominal cavity have pair of testis that makes testosterone similar to males.

Question 39

How does a person appear female but have a Y and testis that make testosterone?

Answer 39

The SRY gene causes testis to develop and produce testosterone Normally testosterone makes tissues develop male characteristics by binding and activating the androgen receptor People with Androgen-Insensitivity Syndrome are defective in this androgen receptor, leading to female characteristics

Question 40

Androgen receptor gene is located on the

Answer 40

X chromosome and is inherited from the mother