Topic 11 pt 1: Sex Chromosomes Flashcards

1
Q

What are autosomes? What kind of ratios do they show

A

Non-sex chromosomes (not X or Y) carry the majority of genes
Show normal mendelian ratios for monohybrid, dihybrid and test crosses

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2
Q

How do we tell if a gene is autosomal

A

Perform a reciprocal cross, do we get mendelian ratios?

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3
Q

Most organisms have how many sexual phenotypes? What are they (usually)

A

Two:
- male: small and numerous gametes
- female: large and limited gametes

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4
Q

What is the XX-XY chr system? Who uses it

A

Humans, flies, most mammals, some plants

Homogametic = female
heterogametic = male

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5
Q

What is the ZZ-ZW chr system? Who uses it?

A

Birds, some reptiles, butterflies
Male = homogametic
Female = heterogametic

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6
Q

Mechanism by which sex is established is termed

A

Sex determination (e.g. XX/XY, ZZ/ZW)

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7
Q

What is the XX-X0 chr system? Who uses it

A

Insects, worms

XX = females or hermaphrodites
X0 = males missing a chr (heterogametic)

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8
Q

Who has no sex chromosomes, only sex-determining genes. This is called

A

Genic sex determination (on various autosomes)

Some plants, fungi, protozoans, fish

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9
Q

What are some ways that sex is determined in nature

A

Temperature (or other environmental conditions e.g. turtles, alligators)

Nutrient status (poor = usually male, rich = female)

Population density

Age

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10
Q

Describe sex determination in the slipper limpet

A

Lone larva settle as female
She releases a chemical to attract more larva, which settle on top of female, become male
Limpets at bottom are female

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11
Q

Are all sex related traits found on the sex chromosomes (in ppl)

A

No
Some genes for non-sex traits are on sex chromosomes

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12
Q

In humans, who determines the sex of the offspring

A

Males

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13
Q

What is the male determining gene in ppl

A

Sex determining region Y, located on y chr
Turns on genes needed to be male

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14
Q

Characteristics of the X chromosome in humans

A

Contains many genes and is essential (at least one)

Y has few genes

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15
Q

Where are fertility genes located

A

Both X and Y

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16
Q

Examples of additional X’s occurring in humans

A
  1. XXY = klinefelter’s syndrome (male phenotype, physiologically normal)
  2. X0 = turners syndrome (female phenotype, not fertile)
  3. XXX = poly X (physiologically normal)
  4. Y0 = impossible
17
Q

Slide 14

A

Confused