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general bio 2024 > lecture 10 > Flashcards

lecture 10 Flashcards

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Biology 101 flashcards
1
Q

What does meiosis produce?

A
  • Cells that differ genetically from the parents and also from each other
  • results in genetically different offspring
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2
Q

Why did sex evolve?

A
  • Allows mixing & matching of genes to produce a genetically novel individual
  • environment constantly changes
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3
Q

Why is diversity of sex important?

A

Increases the possibility of producing an individual that is better able to survive

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4
Q

Asexual reproduction

A
  • In bacteria, archaea,fungi, most algae and many plants
  • quick & easy(high reproductive rate)
  • all offsprings are clones
  • all genes get passed to your offspring
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5
Q

What can break up adaptive combinations of genes?

A

Mixing and matching alleles

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6
Q

Advantages of sex

A
  • Help repair of damaged DNA by copying intact sequence on the other chromosome
  • permits elimination of deleterious mutations
  • provides variation to help in defense against pathogens and parasites
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7
Q

Human somatic cells

A
  • Any other cell than gamete
  • 23 pairs of chromosomes
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8
Q

Karyotype

A

Ordered display of the pairs of chromosomes from a cell

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9
Q

Homologous chromosomes

A
  • Two chromosomes in each pair
  • homologs
  • same length, shape
  • carry genes controlling the same inherited characters
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10
Q

Stage of meiosis

A

1.meiosis I
2. Meiosis ll

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11
Q
  1. Meiosis l
A
  • Reductional division
  • homologs pair up and separate
  • result in 2 haploid daughter cells with replicated chromosomes
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12
Q
  1. Meiosis ll
A
  • equational division
  • sister chromatids separate
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13
Q

Result of meiosis

A
  • Four haploid daughter cells with unreplicated chromosomes
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14
Q

Meiosis 1 (stages)

A
  1. Interphase
  2. Early prophase l
  3. Late prophase l
  4. Metaphase I
  5. Anaphase I
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15
Q
  1. Interphase (meiosis)
A
  • Chromosomes replicate in parent cell, in uncondensed state
  • forms sister chromatids
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16
Q
  1. Early prophase l
A
  • Chromosomes condense
  • nuclear envelope breaks up
  • spindle apparatus forms
  • synopsis of homologous chromosomes
17
Q
  1. Late prophase l
A
  • Crossing over of nonsister chromatids
  • often multiple cross-overs between same chromatids
18
Q
  1. Metaphase l
A
  • Migration of tetrads to metaphase is complete
19
Q
  1. Anaphase l
A
  • Homologs separate
  • begin moving to opposite sides of cell
20
Q

Meiosis ll (stages)

A
  1. Telophase l and cytokinesis
  2. Prophase ll
  3. Metaphase ll
  4. Anaphase Il
  5. Telophase ll and cytokinesis
21
Q
  1. Telophase l and cytokinesis
A
  • Chromosomes move to opposite sides of cell
  • cell divides
22
Q
  1. Prophase ll
A
  • Spindle apparatus forms
23
Q
  1. Metaphase ll
A
  • Chromosomes line up at middle of the cell (metaphase plate)
24
Q
  1. Anaphase ll
A
  • Sister chromatids separate
  • begin moving to opposite sides of cell
25
Q
  1. Telophase ll and cytokinesis
A
  • Chromosomes move to opposite sides of the cell
  • cen divides
26
Q

How does meiosis increase genetic variation?

A

1) crossing over
2) independent alignment/assortment of chromosomes
3) random fertilization

27
Q

Crossing over

A
  • Exchange of genetic material occurs when homologous chromosomes pair-up during prophase I
  • exchange happens at the chiasmata
  • mixes up parental alleles
  • increase genetic variability of meiotic products
28
Q

Independent alignment (assortment) of enromosomes

A

-at metaphase l each homologous pair is randomly positioned independently of other pairs
- daughter cells have a 50/50 chance of getting either maternal or paternal chromosome for (each of the pairs leach chromosome making up n in the 2n)

29
Q

What dees independent alignment means?

A

Meiosis can produce 2^n different gametes

30
Q

Random fertilization

A
  • There are 8,4 million different eggs
  • there are 8.4 million different sperm
  • 70 million possible genetic combinations for any human offspring
31
Q

Down’s syndrome

A
  • non-disjunction of chromosome 2t
  • results in trisomy 21 (3 chromosomes)
  • related to the age of the mother
32
Q

Polyploid

A
  • Organisms with extra sets (3n,4n, and higher )
33
Q

Polyploidy

A
  • Can prevent meiosis because not all chromosomes will have a homolog
  • anaphase I will not take place

general bio 2024 (22 decks)

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