Chapter 5 Flashcards

1
Q

Sexual Reproduction

A
  • formation of offspring that are genetically distinct from parent
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2
Q

Sex is defined by:

A
  • phenotype of the individual
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3
Q

Sex Determination Mechanisms

A
  1. Chromosomal Sex Determination
  2. Genetic Sex Determining
  3. Environmental Sex Determining
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4
Q

Chromosome theory of inheritance

A
  • genes are located on chromosomes and chromosomes are substrate for gene segregation
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5
Q

_____ said male insects had a strange body in the nuclei= X body

A
  • hunking
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6
Q

_____ said male grasshoppers have a heterochromosome and female grasshopper cells had one more chromosome than males

A
  • McClung
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7
Q

_______ said female mealworms have 20 large chromosomes and males have 19 large and one smaller (Y)

A
  • Stevens
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8
Q

____ said female butterflies have two X chromosomes and males have one X

A
  • WIlson
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9
Q

All mammals chromosomes are:

A
  • XX/XY
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10
Q

In simple systems what is the chromosomal sex determination

A
  • XX for females
  • XO for males
    O=no chromosome
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11
Q

At _____ half sperm receive X and other half gets no chromosome

A
  • meiosis
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12
Q

Heterogametic sex

A
  • sex that produces two different gametes
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13
Q

Homogametic sex

A
  • sex that produces identical gametes
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14
Q

What is a ZZ/ZW chromosome sex determination?

A
  • male is homogametic (ZZ)
  • female is heterogametic (ZW_
  • female produces two diff gametes, half with Z other half with W
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15
Q

In haplodiploidy what is the result?

A
  • males are haploid (1n) bc develop from unfertilized eggs
  • females are diploid (2n)
  • sex is determined by the number of chromosome sets
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16
Q

Are there any sex chromosomes in genetic sex determination?

A
  • no, there is no obvious difference
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17
Q

In genetic sex determination what determines the sex of the individual?

A
  • genes
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18
Q

In environmental sex determination what is it dependent on? Give example

A
  • temperature dependent

- alligators in warm temperatures during embryonic development produces males and in cool weather will produce females

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19
Q

Nondisjunction

A
  • When the X chromosome fails to separate in Anaphase 1 of meiosis
  • some eggs get two copies of XX and others get more
20
Q

Sex determination in Drosophilia

A
  • Females XX, males XY, but Y does not determine maleness
  • the ratio of autosomes to X determine the sex = genic balance system
  • X has female producing genes, and autosomes have male producing genes
21
Q

In drosophilia what is sex determined by?

A
  • the X:A ratio (# of X chromosomes/ # of haploid sets of autosomes)
22
Q

Turner Syndrome

A
  • females don’t undergo puberty, immature secondary female characteristics
  • low hairline and folds of skin on neck
  • may have cognitive impairment or sterility
  • XO
  • also known as 45, X
23
Q

Klinefelter Syndrome

A
  • males
  • small testes, breast enlargement, reduced facial/pubic hair
  • one or more Y chromosome, multiple X chromosomes
  • often sterile, may have mild cognitive impairment
  • also known as 47, XXY
24
Q

Poly-X Females

A
  • Triplo-X syndrome (XXX)
  • tall, thin, sometimes normal fertility, normal intelligence
  • XXXX, XXXXX has normal female anatomy, but cognitive impairment
  • severity increases in # of X chromosomes
25
How many X are required for each sex?
- X contains genetic info essential for both sexes | - one is required for each
26
Male determining gene is located on which chromosome?
- Y chromosome
27
What does the absence of Y indicate?
- a female
28
What chromosomes are the genes required for fertility on?
- the X and Y chromosomes | - females need at least 2 to be fertile
29
What happens with extra X chromosomes?
- it is detrimental, the more X chromosomes the more severe
30
What is the purpose of the SRY gene?
- this gene triggers men to develop both male phenotypes and genotypes - if lacking this gene can have XY genotype, but will develop female phenotypes such as female reproductive systems - ONLY found in males with XY - no females (XX OR XY) have this gene
31
What hormones do the SRY gene secrete?
1. anti-mullerian hormone to inhibit and block female reproductive systems from developing 2. testosterone- triggers the male characteristic developments
32
Androgen-insensitivity syndrome
- have female sexual characters, but no uterus, ovaries or oviducts - these women are XY
33
where is pseudoautosomal region 1?
- at the tip of the short arm
34
where is pseudoautosomal region 2?
- at the bottom of the long arm
35
What is the pseudoautosomal region?
- a region of homology between the mammalian X and Y chromosomes - in between the PAR 1 and 2 there is a differential region of the X(Xlinked genes) and Y (Ylinked genes) - on the Y gene there is also the maleness gene SRY on the short arm below PAR 1
36
How does androgen-insensitivity syndrome occur?
- SRY triggers teste development - the testes secrete testosterone - if there is no receptor for testosterone (or defective receptor), then no male characterisics - defect ends up on X chromosome
37
Where are the genes for males and female secondary characteristics located?
- on the autosomes (control of expression is key)
38
What is dosage compensation?
- how to deal with multiple Xs
39
How does dosage compensation affect fruitflies, worms and placental mammals?
- fruitflies double the activity of genes on X in males - worms (C. elegans) halves activity of genes on both Xs - placetal mammals inactivate one X chromosome
40
______ observed darkly staining body in nuclei of cat cells
- Barr | - Barr body
41
_____ proposed that Barr body was inactivated X chromosome
- Lyon | - called Lyon hypothesis
42
X-inactivation
- females are heterozygous at X loci, will express one allele or the other in a given cell
43
What is a barr body?
- the inactivated X chromosome in females
44
Females are _____ for expression of X-linked genes
- mosaic
45
X inactive specific transcript (XIST) gene
- located on X chromosome and is required | - only the copy of XIST on inactivated X is expressed and is expressed during inactivation
46
What is an example of X inactivation? (hint cherokee)
- Two alleles for orange coat X+(black) X-(orange) - Male X+Y (so black OR orange, not both) - Female X+X+(black), X-X-(orange) BUT when X+X- (BOTH are expressed) -> tortoiseshell
47
What is a name for a mosaic cat?
- tortoiseshell