Topic 11-1 Flashcards
refers to sexual phenotypes (anatomical or physiological traits)
biological sex
category assigned by the individual (identity) or others based on behavioural and cultural practices
gender
many organisms are hermaphrodites; this means that:
the organism has both male and female sex organs
biological mechanisms that regulate sexual phenotypes (chr, genetics, environment)
sex determination
in chromosomal sex-determining systems, teh genome consists of:
- autosomes: non-sex chromosomes
- sex chromosomes: distinct in males and females
XX-XY species:
most common system, generates 1:1 ratios of sex phenotypes
female: XX
male: XY
Y chr is not actually Y-shaped, but is:
acrocentric - one chr arm is much shorter than the other
the sex chr pair during metaphase (meiosis I) bc they are homologous in small regions called:
pseudoautosomal regions
what is the heterogametic sex?
the sex that makes two types of gametes (ex: X or Y)
what is the homogametic sex?
the sex that makes all the same gametes (ex: all X)
XX-XO system
simplest sex determination, generates 1:1 ratios of sex phenotypes
females: XX
males: XO
ZZ-ZW system
females: ZW
males: ZZ
for chromosomal sex-determining systems, sex is determined by:
individual genes locates on these sex chr working in conjunction w/ genes on autosomes
genotypes at one or more loci determine the sex of an individual w/out specific sex chr
genic sex determination
what are two examples of organisms that determine sex based fully or in part on environmental factors
mollusks and reptiles
true or false: male mollusks can change sex after mating
true
each individual can be both male and female, but not at the same time
sequential hermaphroditism
in many turtles, crocodiles, alligators, and a few birds, sexual phenotypes are affected by _________ during embryonic development
temperature
Calvin Bridges proposed that in fruit flies sex was determined not by the amount of X and Y chr, but a balance b/w:
- female-determining genes on X
- male-determining genes on the autosomes
- X:A ratio
human males contain a gene known as the _____ gene, which is the located on the Y chromosome
sex-determining region Y gene (SRY gene)
what are the five main roles of sex chr in humans?
1) X chr contains genes essential for both sexes
2) male-determining gene on the Y
3) abscence of Y leads to female sex
4) fertility genes located on both X and Y
5) additional X chr can upset normal development of males and females
describe Turner’s syndrome:
- genotype: XO
- 1:3000 births
- female w/ underdeveloped secondary sex characteristics
- normal intelligence
describe Klinefelter syndrome:
- genotype: XXY or XXXY
- 1:1000 male births
- men w/ small testis, reduced facial and pubic hair, sterile, tall
- normal intelligence
describe androgen-insensitivity syndrome
have normal male chr (XY) but have female external sexual characteristics (vagina but no uterus, oviducts, or ovaries). inside abdominal cavity have pair of testis that have defective androgen receptors, so while testosterone is made, the tissues do not receive the signal and female characteristics develop
what are sex-linked genes?
genes found on the sex chr
does recombination happen in females w/ XX?
yes
does recombination occur in males w/ XY?
yes
true or false: in males, most of the genes on the X chr have only one allele/copy
true
what does it mean to be hemizygous?
possessing only one copy of a gene
swapping the sex of the parental phenotypes is called making a:
reciprocal cross
for autosomal linked genes, reciprocal crosses give:
same proportions of genotypes/phenotypes
for sex-linked genes, reciprocal crosses give:
very different progeny
Bridges hyptohesized that the exceptional white-eyed female flies had ______. this could occur through a process called ______.
two X chr and one Y, nondisjunction
failure of homologous chr or ssiter chromatids to separate in meiosis or mitosis
nondisjunction
red-green colour perception is a ________ trait in humans
recessive, X-linked
in order for human females to develop colour blindness, they have to:
inherit mutant X alleles from both parents
in order for human males to develop colour-blindess, they have to:
inherit the mutant X allele from their mother
sex-linked traits can have multi-generational effects;
1) trait can alternate which sex has the phenotype
2) trait can skip a generation
