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Cell Biology > Lec 23: Meiosis > Flashcards

Lec 23: Meiosis Flashcards

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1
Q

Asexual reproduction

A

Offspring arise from a single parent: includes budding, binary fission, and parthenogenesis

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2
Q

Sexual reproduction

A

the genome of two individuals are mixed to produce an individual that is genetically distinct from its parents

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3
Q

diploid

A

a cell or organism that contains two sets of homologous chromosomes, one inherited from each parent. Cells that reproduce sexually are typically diploid, and have two copies of each gene

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4
Q

homologs

A

a gene, chromosome, or any structure that has a close similarity to another as a result of common ancestry. The maternal and paternal versions of each chromosome are homologs

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5
Q

gametes

A

Cell type in a diploid organism that carries only one set of chromosomes and is specialized for sexual reproduction. (sperm or egg cell, also called a germ cell)

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6
Q

haploid

A

cell or organism with only one set of chromosomes, such as a sperm cell or bacterium

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7
Q

zygote

A

fertilized egg cell; has homologous chromosomes from both the mother and the father

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8
Q

germ line

A

the lineage of reproductive cells that contributes to the formation of a new generation of organisms, as distinct from somatic cells, which form the body and leave no descendants in the next generation

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9
Q

somatic cells

A

any cell that forms part of the body of a plant or animal that is not a germ cell or germ-line precursor

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10
Q

Benefits of sexual reproduction

A

1) produces offspring that are genetically diverse (produces novel chromosome combinations)
2) allows for a chance to remove harmful alleles from the species without ending that genetic line

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11
Q

allele

A

alternative forms of a gene; for a given gene, many alleles may exist in the gene pool of a species

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12
Q

homologous recombination

A

mechamisms by which double-stranded DNA breaks can be repaired flawlessly using a undamaged, dupliucated, or homologous chromosome to guide the repair.

During meiosis, it results in an enschange of genetic material between the maternal and paternal homologs (see crossing over)

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13
Q
A

A) yes, because blood stem cells are somatic cells, and do not contributes genetic material to the next generation. Only germ-line cells which give rise to gametes pass their genetic material on to offspring.

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14
Q
A

Somatic cells do not undergo meiosis. Only cells in the germline undergo meiosis to produce haploid gametes

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15
Q

meiosis definition/ general steps

A

specialized type of cell division by which egg and sperm cells are made. Two successive nuclear divisions with only one round of DNA replication generates four haploid cells from an initial diploid cell

1) normal duplication
2) split in meiosis
a) meiotic prophase(meisosis I): each duplicated paternal chromosome locates and then attaches itself along its entire length to the corresponding duplicated maternal homolog.
b) meiosis II: the two duplcated chromosomes within each haploid are separated producing four haploid nuclei (chromosome segregation is random, so each hapoid gamete will receive a different mixture of maternal and paternal chromosomes

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16
Q

pairing

A

during meiosis, the process by which a pair of duplicated chromosomes attach to one another to form an aligned, linear structure containing four sister chromatids

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17
Q

mitosis vs meiosis I

A
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18
Q

crossing over

A

process where two homologous chrmomosomes break at corresponding sites and rejoin to produce two recombined chromosomes that have physically exchanged segments of DNA

Also helps ensure that the maternal and paternal homologs willl segregate from one another correctly at the first mitotic division

Only happens between the same chromosomes, and only happens at a few places on each chromosome

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19
Q

How many different gametes could an individual produce?

A

One answer: 2^n (n being the number of chromosomes, because those are shuffled randomly). However, with crossing over, the answer is much higher.

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20
Q

fertilization

A

fusion of two gametes (egg and sperm) to form a new cell with a diploid set of chromosomes. There are mechanisms to prevent more than one sperm from fertilizing an egg

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21
Q
A

meiotic phase I only

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22
Q
A

D) begins with a single round of DNA replication, followed by two rounds of cell division

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23
Q

Mendel’s studies of inherited traits

A

They apply to all sexually reproducing organisms. He studied discretely inheritable traits that were easily observable.

His major contribution was to propose that each plant inherited two copies (or alleles) of each gene. Suggested that one was dominant and one was recessive

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24
Q

genotype

A

the genetic makeup of a call or organism, including which alleles (gene variants) it carries

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25
Q

homozygous

A

possessing two identical alleles for a given gene

26
Q

heterozygous

A

possessing dissimilar alleles for a given gene

27
Q

phenotype

A

the observable characteristics of a cell or organism

28
Q

How crossing over affects inheritance

A

Crossing over means that even genes on the same chromosome can be sorted and inherited independently, particularly if they are far apart. Genes that are close together are more likely to be inherited together

29
Q

loss-of-function mutation

A

When the mutation causes a protein not to be made. These are usually recessive, because having another copy of the gene that’s normal can allow the organism to compensate

30
Q

gain-of-function mutation

A

increases the activity of a gene or it’s product, or results in the gene being expressed in inappropriate circumstances. Usually a dominant trait

31
Q
A

the green-pea allele

32
Q
A

They can be present in phenotypically normal individuals

33
Q

Genetics

A

the study of genes, heredity, and the variation that gives rise to differences between one living organism and another

34
Q

Classical genetic approach

A

a set of experimental techniques through which mutations are used to identify the genes responsible for an interesting phenotype

35
Q

complementation test

A

genetic experiment that determines whether two mutations that are associated with the same phenotype lie in the same gene or in different genes

36
Q
A

genetic screen: allows investigators to examine thousands of organisms to find those that exhibit an interesting phenotype

37
Q

polymorphism

A

DNA sequence for which two or more variants are present at high frequency in the general population

38
Q

single-nucleotide polymorphism

A

most polymorphisms are due to the substitution of a single nucleotide

39
Q

haplotype blocks

A

a combination of alleles or other DNA markers that has been inherited as a unit, undisturbed by genetic recombination, for many generations. The longer a particular mutation has been in the human genome, the shorter the haplotype block around it: there are more opportunities for crossovers that might happen close to the mutation. This lets us trace ancestry

40
Q

monogenic disorders

A

ones that arise from a single gene (i.e. sickle cell anemia)

41
Q

multigenic disorders

A

disorders that are caused by a complex combination of many different genes as well as the environment

42
Q
A

SNPs are more common in a population

43
Q
A

They tend to be found in a larger haplotype block

44
Q

Chiasma

A

the points where sister chromatids cross over

45
Q

recombination

A

The result of crossing over

46
Q

What is the main benefit of sexual reproduction?

A

Greatly enhanced opportunities for the creation of new genomes

47
Q

Without crossing over, how many new genome recombinations can be made from meiosis?

A

2^n (n is the number of chromosomes)

for people: 2^23 = 8.4 million

48
Q

When do germ-line cells differentiate from somatic cells? (and why?)

A

Early on in the process. This helps prevent mutations in the somatic cells from being passed on to germ-line cells

49
Q
A

Because the recombination events would lead the daughter cells to have a different genome than the mother cells.

Also, this would result in the cells having two identical (before crossover events) chromosomes in each cell instead of one maternal and one paternal, also leading all the cells to be different.

50
Q

What is the major mechanistic difference between mitosis and meiosis?

A
51
Q

Anaphase 1 in meiosis

A
52
Q

Anaphase 2 in meiosis

A
53
Q

What can go wrong with chromosome division during meiosis?

A

Many of the aneuploid gametes won’t survive, but some can

54
Q

How does location on the chromosome affect cross over events? (and chances of independent inheritance)

A
55
Q

F1 and F2 generations of crosses between plants (single trait being looked at)

A
56
Q

F1 and F2 generations of crosses between plants (two traits being looked at)

A
57
Q

Independent assortment of genes on the same chromosome

A
58
Q

What are the different classes of mutations?

A
59
Q
A

Dominant: always being on means it will always express that phenotype

60
Q
A

Recessive: there is still a working copy that can turn on.

There is something called halpoid insufficiency: the expression of the gene might not be quite enough, so the cell might grow a little less, and the signaling pathway might be a little slower

61
Q

What are two ways we can do modern human genetics?

A

Can’t knock out genes and experiment!

1) Linkage (look at big families over multiple generation)
2) Association (sequence everyone and look at patterns)

62
Q

SNPs

A

Single nucleotide polymorphisms

These most likely happen during the replication process

They often happen in blocks (because the block sticks together during recombination events), and looking for over represenation of these SNPs in groups with diseases can help identify the genes affecting that disease

Cell Biology (24 decks)

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