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BIOL 207 (Principles of Genetics) > Topic D: Mitosis and Meiosis > Flashcards

Topic D: Mitosis and Meiosis Flashcards

1
Q

Every species has a characteristic number of _________ and ______________. The number of ____________describes the ploidy of chromosomes

A

Every species has a characteristic number of chromosomes and chromosome sets . The number of sets of chromosomes describes the ploidy of chromosomes

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2
Q

What are homologous chromosomes?

A

In a diploid (2n) cell, every chromosome has a homologue.
Homologous chromosomes have the same genes in the same order, but may have different alleles for a given gene.

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3
Q

Homologous chromosomes are highly _________, but not __________.

A

Homologous chromosomes are highly SIMILAR, but not IDENTICAL.

the same genes may be in the same order, but it may not be the same alleles! (Abc VS. ABc)

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4
Q

3 features used to differentiate chromosomes?

A
  • size
  • centromere position
  • other features (like banding)
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5
Q

Bacteria reproduces asexually by

A

Binary fission, where the chromosome is fully replicated, and then the cell divides in two, allowing a bacterial to make an identical copy of itself.

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6
Q

Why do cells need to divide in multicellular eukaryotes?

A

Mitosis: replenishes old, damaged cells, repairs cells, and divides for growth. Cells must divide to make more copies of itself

Meiosis: to produce gametes/reproductive cells.

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7
Q

DNA replications always precedes ____ _______

A

cell division

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8
Q

DNA replication occurs in the ____ phase, before cell _________

A

DNA replication occurs in the S phase, before cell division

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9
Q

Cell division occurs in 3 different ways:

A
  • Binary fission (bacteria)
  • Mitosis
  • Meiosis
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10
Q

While Mitosis occurs for Eukaryotes both _____ and ______, Meiosis occurs for Eukaryotes only _________

A

While Mitosis occurs for Eukaryotes both DIPLOID and HAPLOID, Meiosis occurs for Eukaryotes only DIPLOID

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11
Q

While mitosis is an _________ _______, Meiosis is a ___________ ___________.

A

While mitosis is an EQUATIONAL DIVISION Meiosis is a REDUCTION DIVISION.

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12
Q

DNA must be fully replicated before Mitosis or meiosis, this occurs during the :

A

Synthesis (S) phase

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13
Q

What occurs during the S phase?

A
  • DNA content (C) is doubled (DNA is replicated)
  • Ploidy remains unchanged
  • chromosome number remains unchanged
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14
Q

Mitosis is an equational division, where …..

A
  • ploidy does NOT change
  • two daughter cells are produced that are identical
  • both haploid and diploid cells can undergo mitosis
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15
Q

Meiosis is a reduction division, where….

A
  • Ploidy is reduced from 2n to n
  • 4 meiotic products are produced
  • typically, only diploid cells can undergo meiosis
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16
Q

Cell division changes the _____ ______ in a diploid cell

A

DNA CONTENT

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17
Q

By the end of Meiosis DNA content is C= ___. DNA content is halved in meiosis 1 from C=____ to C=____. DNA content is halved once more in meiosis 2 from C=____ to C=____.

A

By the end of Meiosis DNA content is C= 1. DNA content is halved in meiosis 1 from C=4 to C=2. DNA content is halved once more in meiosis 2 from C=2 to C=1.

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18
Q

During Mitosis, a cell divides to produce;

A

two daughter cells with the same ploidy and chromosome number

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19
Q

in mitosis, the only change we see is a _____ in ____ ____

A

in mitosis, the only change we see is a REDUCTION in DNA CONTENT.

20
Q

What are the four major stages of mitosis?

A
  • prophase
  • metaphase
  • anaphase
  • telophase and cytokinesis
21
Q

in mitosis, what occurs during prophase?

A

This is where chromosomes condense

22
Q

in mitosis, what occurs during metaphase

A

This is where all the chromosomes line up at the “metaphase plate”

23
Q

in mitosis, what occurs during anaphase ?

A

Reduction in DNA content occurs in anaphase
Two sister chromatids joined at a centromere separate and segregate to opposite polls

24
Q

in mitosis, what occurs during telophase/cytokinesis ?

A

This is where division of the cell is completed

25
Q

Meiosis produces:

A

4 haploid cells with a single copy of each chromosome, where the DNA content is 1

26
Q

Specialized cells called _______ can undergo meiosis, ex. ____ and ______

A

Specialized cells called meiocytes can undergo meiosis, ex. oocytes and spermatocytes

27
Q

there are 2 successive nuclear divisions in meiosis, describe them

A

Meiosis 1: reduction division, ploidy will be reduced from 2n to n

Meiosis 2: equational division, ploidy starts at n and stays at n

28
Q

What occurs in Prophase 1?

A
  • Homologous chromosomes synapse (zippered together) to form bivalents (tetrades)
  • Once synapse occurs, crossing over between non-sister chromatids within a bivalent occurs.
  • Crossing over is an EQUAL exchange of DNA sequence between non-sister chromatids in the bivalent. Crossing-over allows genetic information to be recombined and the new combinations of genetic sequence are a mechanism for generating genetic diversity
29
Q

What occurs in metaphase 1?

A

Bivalents line up at the metaphase plate (middle of the cell)

30
Q

What occurs in anaphase 1?

A
  • Homologous chromosomes in the bivalents separate and move to opposite polls
  • Reduction in ploidy from 2n to n
  • Reduction in chromosome number (by half)
  • Reduction in DNA content (c) from 4c to 2c
31
Q

What occurs in anaphase 2?

A
  • Sister chromatids separate and segregate to opposite polls
  • Chromosome number does not change
  • DNA content is reduced from 2c to 1c
32
Q

What is Mendel’s first law of equal segregation? How does it relate to meiosis?

A
  • When an organism makes gametes, each gamete receives just one gene copy, which is selected randomly. This is known as the law of segregation
  • This law deals with one gene only
  • Alleles of a gene segregate from each other in meiosis (anaphase 1)
  • Homologous chromosomes segregate equally from one another during meiosis
  • Therefore, the two alleles of a gene, one present on each homolog, segregate equally from one another during meiosis

Ex. if a diploid cells with the genotype Aa undergoes meiosis
50% A gametes
50% a gametes
(EQUAL SEGREGATION OF A GENE)

33
Q

What is Mendel’s second law of independent assortment ? How does it relate to meiosis?

A
  • Different chromosomes assort independently of one another
  • Therefore, the allele of different genes assort independently of one another
  • This law deals with different genes on different chromosomes (which act independently)

Ex. gene A and B are on different chromosomes
If a cell with the genotype AaBb undergoes meiosis
Probability that a gamete is A= 50%
probability that a gamete is B= 50%
Probability that a gamete is A and B= 25% (0.50 x 0.50 = 0.25)

34
Q

errors (mutations) during meiosis can result in changes to:

A
  • chromosome number
  • ploidy
  • chromosome structure
35
Q

What is a euploid?

A

an organism with the typically number of chromosomes for their species (ex. humans = 46)

35
Q

What is Aneuploidy? what is it the result of? What can it result in?

A
  • Mutation that results in a change in the number of chromosomes
  • Is the result of nondisjunction during meiosis, where chromosomes fail to segregate at anaphase. Can occur during anaphase 1 or 2
  • Aneuploid gametes usually not viable and can result in early pregnancy losses
35
Q

What can changes in ploidy due to mutation result in? how do they occur?

A
  • ploidy changes can occur spontaneously or induced through exposure to mutagens
  • Changes in ploidy may result in new species in a single generation! Typically speciation occurs over a long evolutionary timescale. But changes in ploidy due to mutation can produce a new species in a single generation.
36
Q

What are the four types of changes in chromosome structure due to mutations?

A
  • translocations
  • inversions
  • duplications
  • deletions
37
Q

What is a translocation? (changes in chromosome structure due to mutations)

A

where a segment of one chromosome ends up being attached to a different chromosome.

ex.
WT: A-B-C-D-E-F-G
MUT: A-B-C-D-E-Q-R

38
Q

What is an inversion? (changes in chromosome structure due to mutations)

A

where a segment of the chromosome ends up in the wrong orientation, Locus is changed

ex.
WT: A-B-C-D-E-F-G
MUT: A-B-D-C-E-F-G

39
Q

What is a duplication? (changes in chromosome structure due to mutations)

A

Additional genes added/duplicated to a DNA sequence , where DNA sequence information is duplicated. this may cause overexpression!

ex.
WT: A-B-C-D-E-F-G
MUT: A-B-C-D-E-D-E-F-G

40
Q

What is a deletion? (changes in chromosome structure due to mutations)

A

one or more genes being deleted from a DNA sequence.

ex.
WT: A-B-C-D-E-F-G
MUT: A-B-C-F-G

41
Q

Changes in chromosome number and structure may impact ______ _______

A

cell function

42
Q

If Changes in chromosome number and structure occur in germline cells …..

A
  • Can result in non-viable gametes, or early pregnancy losses
  • Can alter the phenotype of the next generation in a variety of ways
  • May be silent
43
Q

If Changes in chromosome number and structure occur in somatic cells …..

A
  • may impact cell function
  • may be silent

BIOL 207 (Principles of Genetics) (8 decks)

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