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Science of Repro > Chromosomes and Genes > Flashcards

Chromosomes and Genes Flashcards

1
Q

What is the defining feature of all evolving living organisms

A

The ability to reproduce

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2
Q

Karyotype

A

number and appearance of human chromosomes

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3
Q

For genes to be functional DNA must be able to (three things)

A
  • replicate
  • separate its 2 copies at mitosis
  • maintain itself between generations
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4
Q

Chromosome Abnormalities

Monosomy

A

Missing Chromosomes

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5
Q

Chromosome Abnormalities

Trisomy

A

Extra Chromosomes

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6
Q

Down Syndrome

A

Trisomy 21

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7
Q

Turner Syndrome

A

45X

One X no Y or X

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8
Q

Klinefelter syndrome

A

47XXY

Extra X

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9
Q

Edwards Syndrome

A

Trisomy 18

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10
Q

Patau Syndrome

A

Trisomy 13

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11
Q

Androgens -> Oestrogens

Through which enzyme?

A

Aromatase

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12
Q

Where is Aromotase made?

A

Granulosa cells (follicles)

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13
Q

Theca Cells is where

A

Androgens are produced

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14
Q

How can the same gene be tissue specific

A

By having alternative promoters

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15
Q

Menopause

A

No follicles/eggs/ovarian functions

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16
Q

How can one gene give rise to several products?

What are the products known as?

A

Alternative splicing of exons

Isoforms

17
Q

How can the protein be modified once made?

A

Post-translational modification eg phosphorylation

Glycosylation i.e. adding on carbohydrates to protein, making protein more stable and soluble

18
Q

What are the DNA requirements for sexual reproduction?

A

Fusion of haploid cells (gametes) to create unique diploid progeny

19
Q

What are the advantages of sexual reproduction?

A

Prevents the accumulation of genetic mutations

Increase in genetic diversity

Maintenance occurs because of the advantage of genetic variability

Better able to evolve and adapt to changing environment due to variation

20
Q

Gamete

A

A haploid cell specialised for sexual fusion

21
Q

Gametes are highly specialised cells originating from which kind of cells?

A

Primordial Germ Cells

Gametes are formed from germ line cells: primordial germ cells that migrate into the gonad and then differentiate to either male or female gametes.

oogenesis ? spermatogenesis?

Undergo cycles of mitosis to increase numbers

Then undergo meiosis

Then combine at fertilisation

22
Q

Comparison of Mitosis & Meiosis

Mitosis?

*Involves ___ cell division
*Produces _______ ______ cells
*Occurs in ________ cells
*Results in _____ ___ _______
*Genetic material exchanged?
*Are daughter cells genetically similar?

A

*Involves one cell division
*Produces two diploid cells
*Occurs in somatic cells
*Results in growth and repair
*No exchange of genetic material
*Daughter cells are genetically similar

23
Q

Comparison of Mitosis & Meiosis

Meiosis?

*Involves ___ cell division
*Produces up to _______ ______ cells
*Occurs in ________and _______
*Results in _____
*Genetic material exchanged?
*Are daughter cells genetically similar?

A

*Involves two cell divisions
*Produces up to four haploid cells
*Occurs only in ovaries and testes during the formation of gametes (egg and sperm)
*Results in gamete (egg and sperm) production
*Parts of chromosomes are exchanged in crossing over
*Daughter cells are genetically dissimilar

24
Q

Why is meiosis advantageous?

A
  • Random distribution of male and female homologous chromosomes
  • chromosomal crossing over occurs
25
Q

How is genetic variability achieved?

Two ways

A

Independent Assortment

Crossing Over (Recombination)

26
Q

Independent Assortment

A

Homologous pairs of chromosomes line up at the equator (midpoint) of the spindle during metaphase I.

However, the orientation of the members of the pair is random with respect to which member is closer to which pole.

27
Q

Crossing Over (Recombination)

A

Corresponding pieces of chromatids of maternal and paternal homologues (non-sister chromatids) are exchanged during synapsis when the homologues are aligned side by side.

Each of the affected chromatids has a mixture of maternal and paternal genetic information

28
Q

Does Crossing Over of Sex Chromosomes occur?

A

Sex chromosomes align but crossing over does not usually occur in X and Y chromosomes apart from at the pseudoautsomal regions (PAR)

29
Q

why doesn’t Crossing-over of sex chromosomes not usually occur?

A

They are hemizygous to each other & so recombination proved harmful
PAR allows the X & Y chromosomes to pair and properly segregate during meiosis in males

30
Q

aneuploidy

A

A gain or loss of chromosomes from the normal 46

31
Q

Non-disjunction

A

Failure of homologous chromosome to separate during MI or sister chromatids to separate during MII, resulting in extra or missing chromosomes

32
Q

Most common aneuploidies in humans are _____

A

trisomies

33
Q

Increase in Maternal Age

A

Increases risk of Trisomy

34
Q

What are the factors of maternal age and risk of trisomy effect

A

Recombination failure

Premature homologue separation

Premature sister chromatid separation due to loss of cohesion between sister centromeres

Science of Repro (15 decks)

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