BIOL2030 > Module 3 > Flashcards

Module 3 Flashcards

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1
Q

Types of cells involved in sexual reproduction?

A

Sexual reproduction: alternation between haploid and diploid cell types (most eukaryotes)

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2
Q

What is sexual reproduction?

A

Sexual reproduction: process of organism reproduction that results in offspring that are genetically distinct from their parents.
- We do this through independent assortment and crossing over events.

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3
Q

What is sex?

A

Sex: the phenotype of sex; a classification system based on biological differences between males and females rooted in anatomy or physiology.

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4
Q

What is monoecious?

A

Monoecious: the condition of having both male and female reproductive structures in the same organism

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5
Q

What is Diocious?

A

Dioecious: species of organisms that have either male or female reproductive structures.

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6
Q

What are 4 types of sex determination?

A
  1. Chromosomal sex determination
  2. Genetic sex determination
  3. Environmental sex determination
  4. Haplodiploidy
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7
Q

How is sex defined?

A

Sex: a classification based on biological differences between males and females rooted
in their anatomy or physiology.

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8
Q

How is gender defined?

A

Gender: a classification based on the social construction (and maintenance) of cultural
distinctions between males and females. Gender refers to “a social construct regarding
culture-bound conventions, roles, and behaviors for, as well as relations between and
among, women and men, boys and girls” (Krieger, 2003).

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9
Q

What are the three mechanisms of sex determination?

A
  1. environmental
  2. genetic
  3. chromosomal (& haplodiplody)
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10
Q

What is genetic sex determination?

A

Genetic sex determination: sexual phenotype is determined by genes at one or more loci carried on autosomes. There are no sex chromosomes in this system

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11
Q

Examples of genetic sex determination?

A

Some plants and protozoans

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12
Q

What is environmental sex determination?

A

Environmental sex determination: sexual phenotype is determined in part, or in full, by
environmental factors

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13
Q

Examples of environmental sex determination?

A

Turtles: incubation > 32°C ➔ females
incubation < 28°C ➔ males
32°C > incubation > 28°C ➔ mix

Alligators: warm ➔ males
cool ➔ females

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14
Q

What are autosomes?

A

Autosomes: chromosomes that are the same in males and females

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15
Q

What are sex chromosomes?

A

Sex chromosomes: a pair of chromosomes that differs between females and males

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16
Q

How do sex chromosomes differ between male and female?

A

matched pair in one sex (e.g., human XX) and unmatched in the other (e.g., human XY)
* sometimes only one sex chromosome (e.g., XX versus XO)

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17
Q

Why are human males called heterogametic sex?

A

note: human males are called the “heteorgametic sex” because they produce two “kinds” of haploid gametes (having X or Y chrom.)
X X
X Y

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18
Q

4 steps of evolving a heterogametic sex?

A
  1. start as an autosomal pair
  2. gain sex determining genetic systems
  3. crossing over (recombination) gets suppressed
  4. chromosomes diverge between males and females (Y degeneration)
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19
Q

XX-XY system?

A

Females: XX (homogametic sex)
Males: XY (heterogametic sex)
X egg + X sperm ➔ female
X egg + Y sperm ➔ male

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20
Q

Examples of XX-XY?

A

ex: some insects, plants & reptiles; all mammals
(incl. humans)

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21
Q

XX-XO system?

A

Females: XX (homogametic sex)
Males: X0 (heterogametic sex)
X egg + X sperm ➔ female
X egg + 0 sperm ➔ male

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22
Q

Examples of XX-XO systems?

A

ex: grasshoppers, other insects

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23
Q

ZZ-ZW system?

A

Females: ZW (heterogametic sex)
Males: ZZ (homogametic sex)
Z egg + Z sperm ➔ male
W egg + Z sperm ➔ female

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24
Q

Examples of ZZ-ZW system?

A

Ex: birds; moths; some amphibians and fishes

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25
What is haplodiploidity?
No sex chromosomes System = number of chromosomes Males: haploid (n) Females: diploids (2n)
26
Examples of haplodiploidity?
ex: bees; wasps; ants
27
Size of female gametes?
females produce large gametes by asymmetrical meiosis
28
Size of male gametes?
males produce small (usually motile) gametes
29
Who is heterogametic in the XX-XY, ZZ-ZW and XX-XO systems?
XX-XY = males ZZ-ZW = females XX-XO = males
30
What are primary sex characteristics?
primary sex characteristics: in genetics, this refers to the type of gamete that is made. * In humans, this is sperm vs. egg.
31
What are secondary sex characteristics?
secondary sex characteristics: traits that tend to differ between the sexes of a species, but which are not directly part of the reproductive system.
32
Examples of human secondary sec characteristics?
In humans, examples include height, bone density & structure, muscle mass, fat distribution, facial hair, voice, & some aspects of social behaviour
33
3 Items Involved with sex determination?
1. Sexual development depends on genes on sex chromosomes AND autosomes 2. Most 2° sexual characteristics depend on autosomal genes 3. Sexual phenotype does not depend on the mere presence of genes, but on correct control of gene expression
34
What determines "maleness"
gene on Y (called SRY) determines “maleness”
35
What carries genes essential for both sexes?
X chromosome carries genes essential for both sexes: i. females (usually) need two copies of X for fertility ii. at least one copy of X required for viability (males & females)
36
Which chromosomes carry genes for fertility?
both X and Y carry genes essential for fertility: i. DAZ (Y-encoded) required for sperm development ii. Zfx and DIAPH2 (X-encoded) required for ovarian maintenance
37
What is the role of SRY?
* encodes a protein that binds DNA (transcription factor) * function is to bend DNA * alters expression of other genes that determine testes development * “fundamental” (but not only) determinate of male phenotype * found in all mammals examined to date * genetic engineering: XX mice + SRY ➔ male
38
Where do you find genes for the primary sex phenotype?
Genes involved in development of the 1°sex phenotype are “sprinkled” throughout the human genome (it takes more than just X and Y).
39
Do you need all of the chromosomes to determine primary characteristics?
YES!! Need all to develop sperm and testes. - All of us have them, we control gene expression + regulation will showcase these characteristics in males.
40
How is the human sexual phenotype like a constellation?
The human sexual phenotype is an extremely complex “constellation” of traits (1° and 2° ) that depends on setting the level of expression of many genes located throughout the entire genome.
41
How do X and Y chromosomes pair during meiosis?
They have pseudoautosomal regions near their telomeres, which is how they find one another to match.
42
Pseudoautosomal genes?
Pseudoautosomal genes have autosomal pattern of inheritance - Y-euchromatin genes have Y-linked pattern of inheritance
43
What can sometimes happen during pairing and segregation?
Since X and Y are not (generally) homologous, pairing and segregation can sometimes FAIL: This leads to nondisjunction
44
When can non-disjunction occur?
Non-disjunction can occur at Meiosis I or Meiosis II
45
What is non-disjunction really?
This is due to improper chromosome separation
46
What will happen if nondisjunction occurs in meiosis I?
We have half n + 1 and half n - 1. - None have the NORMAL haploid set, either 3 or 1
47
What results from nondisjunction of sister chromatids in meiosis II?
Only half of the gametes do NOT have the normal haploid set (n). - one will have 1 and one will have 3, whilst 2 will be normal haploid.
48
What happens when someone has turner syndrome?
They will only have one X and no Y. - this is when an n egg and n-1 sperm comes together, forming XO
49
Chromosomes in turner syndrome?
45 chromosomes, XO
50
Chromosomes in triplo-X-syndrome?
47 chromosomes, XXX
51
Chromosomes in Klinefelter syndrome?
47 chromosomes, XXY 48 chromosomes, XXXY 47 chromosomes, XXYY
52
What is dosage compensation?
dosage compensation: mechanism that equalizes the amount of protein produced by X-linked genes between heterogametic and homogametic sexes.
53
Difference in "dosage" between males and females?
males (XY): 1× gene products females (XX): 2× gene products (double “dose” of X-linked genes)
54
Mechanisms of dosage compensation?
1. double the activity of X-linked genes in males (e.g., Drosophila) 2. half the activity of X-linked genes in female (e.g., C. elegans) 3. inactivate genes on one X chromosome in females (e.g., placental mammals)
55
What is a bar body?
Bar body: a mostly inactivated X chromosome in females. * appears as a dark stained “body” in the nuclei of a cell * process of inactivation is called Lyonization
56
Barr bodies in typical male and female?
male = 0 female = 1
57
barr bodies in a person with turner syndrome?
XO = 0
58
Barr bodies in a person with triplo-x-syndrome?
XXX = 2
59
Barr bodies in a person with Klinefelter syndrome?
XXY = 1
60
Barr bodes in a person with Klinefelter (48)?
XXXY = 2
61
Barr bodies in a person with 47 Klinefelter syndrome?
XXYY = 1
62
When does lyonization occur?
occurs about 16 days after fertilization (500- to 1000- cell stage)
63
How does inactivation occur?
inactivation is random (diff. cells, diff. X chrom.)
64
What are females transcriptionally equivalent to?
females transcriptionally equivalent to single male X chromosome
65
what does lyonization yield?
yields functional hemizygosity (at the cellular level after 16 days)
66
genetic mosaics?
50:50 allelic expression: females are genetic mosaics
67
What is x-inactivation due to?
X inactivation due to Xist gene
68
Examples of women being genetic mosaics - dysplasia?
Anhidrotic ectodermal dysplasia: Human X-linked trait characterized by several conditions including skin having no hair and no sweat glands. Heterozygous women have irregular “patches” of affected skin.
69
Patterns of inheritance of sex-linked genes/traits?
1. autosomal genes segregate into gametes independently of X and Y 2. traits encoded by genes on X and Y will be associated with the sex phenotype 3. traits encoded by genes on X and Y have UNUSUAL patterns of inheritance (females can be heterozygous, but males cannot)
70
What is meant by a reciprocal cross?
Reciprocal cross is when you swap which parent has what genotype. X+X+ X-Y becomes X+X- X+Y
71
Autosomal loci inheritance rule?
Autosomal loci: * F2 always 3:1 (dominance) * reciprocal crosses same * males = females = 3:1
72
X-linked loci inheritance rules?
X-linked loci: * F2 not always 3:1 * reciprocal crosses differ * phenotype ratio: males ≠ females
73
Y-linked loci inheritance rules?
Y-linked loci: * NEVER expressed in female * direct ➔ father son inheritance
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