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Fundamental genetics > Chapter 5 > Flashcards

Chapter 5 Flashcards

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Biology 101 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
Q

How many X are required for each sex?

A
  • X contains genetic info essential for both sexes

- one is required for each

26
Q

Male determining gene is located on which chromosome?

A
  • Y chromosome
27
Q

What does the absence of Y indicate?

A
  • a female
28
Q

What chromosomes are the genes required for fertility on?

A
  • the X and Y chromosomes

- females need at least 2 to be fertile

29
Q

What happens with extra X chromosomes?

A
  • it is detrimental, the more X chromosomes the more severe
30
Q

What is the purpose of the SRY gene?

A
  • 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
Q

What hormones do the SRY gene secrete?

A
  1. anti-mullerian hormone to inhibit and block female reproductive systems from developing
  2. testosterone- triggers the male characteristic developments
32
Q

Androgen-insensitivity syndrome

A
  • have female sexual characters, but no uterus, ovaries or oviducts
  • these women are XY
33
Q

where is pseudoautosomal region 1?

A
  • at the tip of the short arm
34
Q

where is pseudoautosomal region 2?

A
  • at the bottom of the long arm
35
Q

What is the pseudoautosomal region?

A
  • 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
Q

How does androgen-insensitivity syndrome occur?

A
  • 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
Q

Where are the genes for males and female secondary characteristics located?

A
  • on the autosomes (control of expression is key)
38
Q

What is dosage compensation?

A
  • how to deal with multiple Xs
39
Q

How does dosage compensation affect fruitflies, worms and placental mammals?

A
  • 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
Q

______ observed darkly staining body in nuclei of cat cells

A
  • Barr

- Barr body

41
Q

_____ proposed that Barr body was inactivated X chromosome

A
  • Lyon

- called Lyon hypothesis

42
Q

X-inactivation

A
  • females are heterozygous at X loci, will express one allele or the other in a given cell
43
Q

What is a barr body?

A
  • the inactivated X chromosome in females
44
Q

Females are _____ for expression of X-linked genes

A
  • mosaic
45
Q

X inactive specific transcript (XIST) gene

A
  • located on X chromosome and is required

- only the copy of XIST on inactivated X is expressed and is expressed during inactivation

46
Q

What is an example of X inactivation? (hint cherokee)

A
  • 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
Q

What is a name for a mosaic cat?

A
  • tortoiseshell

Fundamental genetics (15 decks)

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