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From Flashcardlet > 2 A&P II Chapter 27 Meiosis > Flashcards

2 A&P II Chapter 27 Meiosis Flashcards

1
Q

What does homologous chromosome mean?

A

The chromosomes carry the same genes

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2
Q

What is a gene?

A

A sequence of nucleotides that encodes for a protein; a section of DNA that influences some hereditary trait in an individual

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3
Q

What is an allele?

A

A differnt version of the same gene

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4
Q

Homologous chromosomes carry the same – but each may contain different –

A

Homologs carry the same genes but may contain different alleles

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5
Q

What is karyotype?

A

THe number and type of chromosomes present

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6
Q

What does diploid mean?

A

Cells contain two versions of each type of chromosome

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7
Q

How many alleles does a diploid have?

A

Two alleles of each gene, one on each of the homologous pairs

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8
Q

What does haploid mean?

A

Cells contain just one of each type of chromosome

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9
Q

How many alleles does a haploid cell have?

A

Only one allele of each gene (does not contain homologous chromosomes)

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10
Q

What is the scientific notation for haploid and diploid?

A 
Haploid = n
Diploid = 2n
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11
Q

What does n stand for?

A

The number of distinct types of chromosomes in a given cell

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12
Q

What is ploidy?

A

the combination of the numbers of sets and n is termed the cell’s ploidy

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13
Q

Describe body cells

A

Diploid, 2n, 46 chromosomes, 23 pairs

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14
Q

Describe gametes

A

Haploid, n, 23 total chromosomes (sperm and oocyte)

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15
Q

What is the end result of meiosis I?

A

Each of the two daughter cells has one of each type of chromosome (DOUBLE STRAND) instead of two (1/2 as many chromosomes as the parent cell)

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16
Q

What is the end result of meiosis II?

A

The sister chromatids from each chromosome separate and one chromatid goes to each daughter cell, resulting in cells that have one of each type of chromosome (SINGLE STRAND)

17
Q

When do chromosomes replicate?

A

During S phase of interphase

18
Q

What happens in prophase I

A

Chromosomes condense
Spindle apparatus forms
Nuclear envelope disappears
Homologous chromosome pairs come together (syapsis)

19
Q

What is a tetrad?

A

Each chromosome consists of two chromatids connected by a centromere

20
Q

What is a chiasma?

A

In late prophase I, chromatids begin to separate by stay joined at certain sites, looking as if they cross over one another

21
Q

What do chiasmas result in?

A

Paternal and maternal chromatids break and rejoin at each chiasma producing chromatids that have both paternal and maternal segments

22
Q

What happens in metaphase I?

A

Kinetochore microtubules move the pairs of homologous chromosomes to the metaphase plate, the alignment of maternal and paternal homologs from each chromosome is random

23
Q

What happens in anaphase I?

A

Homologous chromosomes in each tetrad separate and begin moving to the opposite poles of the cell

24
Q

What happens in telophase I?

A

Homologs finish moving to the opposite sides of the cell and the cleavage furrow results in cytokinesis forming two haploid daughter cells

25
Q

What is reduction division?

A

When the cell division results in one chromosome of each homologous pair is distributed to a different daughter cell - cells are haploid

26
Q

Do the daughter cells of meiosis I have un/replicated chromosomes?

A

Replicated chromosomes - they still have two sister chromatids

27
Q

Does replication occur between meiosis I and II?

A

No, just more division

28
Q

What happens in anaphase II?

A

Sister chromatids separate and move to different daughter cells

29
Q

What happens in telophase II?

A

Each chromatid has reached separate daughter cells

30
Q

What is the end result of meiosis II?

A

Four daughter cells each with unreplicated chromosomes

31
Q

What is independent assortment?

A

When pairs of chromosomes line up during meisosi I and the homologs separate a variety of combinations of maternal and paternal chromosomes can result - random assortment

32
Q

How many assortments can diploid organisms produce?

A

2^n - 2^23 or about 8.4 million gametes that differ in their combination of maternal and paternal chromosome sets

33
Q

What does crossing over produce?

A

New combinations of alleles within a chromosome, combinations that did not exist in either parent

34
Q

Why is crossing over important?

A

It dramatically increases the genetic variability of gametes produced by meiosis

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