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General Bio 1 for science majors > Chapter 13 > Flashcards

Chapter 13 Flashcards

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1
Q

What accounts for the resemblance between offspring and parents?

A

Meiosis produces cells with half the chromosomes of the parent cell. It occurs only in specialized cells.

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2
Q

What is fertilization?

A

It unites a sperm and egg, re-establishing pairs of homologous chromosomes with both paternal and maternal genes.

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3
Q

What is heredity?

A

The transmission of traits from one generation to the next is called inheritance, or heredity.

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4
Q

What is the inherited similarity?

A

Sons and daughters are not identical copies of either parent or of their siblings. Along with inherited similarity, there is variation.

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5
Q

What is genetics?

A

The study of heredity and inherited variation.

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6
Q

What are genes?

A

The units of heredity and are made up of segments of DNA. Most DNA is packaged into chromosomes.

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7
Q

What are gametes?

A

Reproductive cells, sperm or eggs, through which genes are passed to the next generation.

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8
Q

What are somatic cells?

A

All cells of the body except gametes and their precursors. They have 46 chromosomes in somatic cell nuclei.

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9
Q

What is the locus?

A

A gene’s specific position along a chromosome.

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10
Q

What is asexual reproduction?

A

A single individual passes all of its genes to its offspring without the fusion of gametes.

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11
Q

What is a clone?

A

An individual or group of genetically identical individuals from the same parent.

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12
Q

What is sexual reproduction?

A

Two parents give rise to offspring that have unique combinations of genes inherited from the two parents.

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13
Q

What is the life cycle?

A

The generation to generation sequence of stages in the reproductive history of an organism. The behavior of chromosomes is related to the human lifecycle and other types of sexual life cycles.

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14
Q

How many pairs of chromosomes do somatic cells have?

A

23 pairs.

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15
Q

What is a karyotype?

A

An ordered display of the pairs of chromosomes from a cell.

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16
Q

What are the two chromosomes in a pair?

A

Homologous chromosomes, or homologs. Chromosomes in a homologous pair have the same length, centromere position, and staining pattern. They also carry genes controlling the same inherited characters.

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17
Q

What are the sex chromosomes?

A

They determine the sex of the individual, X and Y. Human females have a homologous pair of X chromosomes (XX). Human males have one X and one Y chromosome (XY).

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18
Q

What are the autosomes?

A

The remaining 22 pairs of chromosomes that don’t include the sex chromosomes.

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19
Q

What does each pair of homologous chromosome include?

A

One chromosome from each parent. The 46 chromosomes in a human somatic cell are two sets of 23; one from the mother and one from the father.

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20
Q

What is a diploid cell?

A

It has two sets of chromosomes (2n). For humans, the diploid number is 46 (2n = 46).

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21
Q

What is a haploid cell?

A

A gamete contains a single set of chromosomes and is thus a haploid cell (n). For humans, the haploid number is 23 (n = 23). Each set of 23 consists of 22 autosomes and a single sex chromosome.

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22
Q

Where are the sex chromosomes originally located?

A

In unfertilized eggs (ova, um), the sex chromosome is X. In a sperm cell, the sex chromosome may be either X or Y.

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23
Q

What is the fertilized egg called?

A

It’s called a zygote and has one set of chromosomes from each parent. The zygote produces somatic cells by mitosis and develops into an adult.

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24
Q

What organ produces the haploid gametes?

A

In females, the ovaries, and in males, the testes.

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25
What cells use meiosis?
Gametes are the only type of human cell that produce through meiosis.
26
What does meiosis result in?
One set of chromosomes in each gamete. Fertilization and meiosis alternate in sexual life cycles to maintain chromosome number.
27
What does the alternation of fertilization and sexual life cycles have in common?
Alternation of meiosis and fertilization is common to all organisms that reproduce sexually. The three main types of sexual life cycles differ in the timing of meiosis and fertilization.
28
Do gametes undergo cell division before fertilization?
No.
29
How does the multicellular organism develop?
Gametes fuse to form a diploid zygote that divides by mitosis to develop into the multicellular organism.
30
What is the alternation of generations?
The life cycle includes both a diploid and haploid multicellular stage. The diploid organism, called the sporophyte, makes haploid spores by meiosis. Includes plants and some algae.
31
How do spores grow?
Each spore grows by mitosis into a haploid organism called a gametophyte. A gametophyte makes haploid gametes by mitosis, and fertilization of gametes results in a diploid sporophyte.
32
What is different in most fungi and some protists?
The only diploid stage is the single celled zygote, and there is no multicellular diploid stage. The zygote produces haploid cells by meiosis, and each haploid cell grows by mitosis into a haploid multicellular organism. The haploid adult produces gametes by mitosis.
33
What is the same in all three life cycles?
The halving and doubling of chromosomes contribute to genetic variation in offspring.
34
What are the cell divisions of meiosis?
Meiosis I and meiosis II.
35
What happens in both meiosis divisions?
They result in four daughter cells, rather than the two daughter cells in mitosis. Each daughter cell has only half as many chromosomes as the parent cell.
36
What is sister chromatid cohesion?
Chromosomes duplicate before meiosis and the resulting sister chromatids are closely associated along their lengths. The chromatids are sorted into four haploid daughter cells.
37
What are the divisions of meiosis I?
Prophase I, metaphase I, anaphase I, telophase I and cytokinesis.
38
What happens in prophase I?
In early parts of the stage, each chromosome pairs with its homolog and crossing over occurs. X shaped regions called chiasmata are sites of crossovers.
39
What happens in metaphase I?
Pairs of homologs line up at the metaphase plate, with one chromosome facing each pole. Microtubules from one pole are attached to the kinetochore of one chromosome of each pair. Microtubules from the other pole are attached to the kinetochore of the other chromosome.
40
What happens in anaphase I?
Pairs of homologous chromosomes separate. One chromosome of each pair moves toward opposite poles, guided by the spindle apparatus. Sister chromatids remain attached at the centromere and move as one unit toward the pole.
41
What happens in telophase I and cytokinesis?
In the beginning of telophase I, each half of the cell has a haploid set of duplicated chromosomes. Each chromosome still consists of two sister chromatids. Cytokinesis usually occurs simultaneously, forming two haploid daughter cells.
42
During cytokinesis and meiosis, what happens in animal cells and plant cells?
Animal cells form a cleavage furrow, and plant cells form a cell plate. No chromosome replication occurs between the end of meiosis I and the beginning of meiosis II because the chromosomes are already replicated.
43
Simplified parts of prophase I?
Fragments of nuclear envelope, centromeres, centrosome (with centriole pair), pair of homologous chromosomes, spindle microtubules, chiasmata, sister chromatids.
44
Simplified parts of metaphase I?
Kinetochore (at centromeres), kinetochore microtubules, metaphase plate.
45
Simplified parts of anaphase I?
Sister chromatids remain together, homologous chromosomes separate.
46
Parts of telophase I and cytokinesis?
Cleavage furrow.
47
What are the divisions in meiosis II?
Prophase II, metaphase II, anaphase II, telophase II and cytokinesis. Meiosis II is very similar to mitosis.
48
What happens in prophase II?
A spindle apparatus forms. In late prophase II, chromosomes (each still composed of two chromatids) move toward the metaphase plate.
49
What happens in metaphase II?
The sister chromatids are arranged at the metaphase plate. Because of crossing over in meiosis I, the two sister chromatids of each chromosome are no longer genetically identical. The kinetochores of sister chromatids attach to microtubules extending from opposite poles.
50
What happens in anaphase II?
The sister chromatids separate. The sister chromatids of each chromosome now move as two newly individual chromosomes toward opposite poles.
51
What happens in telophase II and cytokinesis?
In telophase II, the chromosomes arrive at opposite poles. In nuclei form, the chromosomes begin decondensing.
52
What is special about the four daughter cells produced by meiosis?
Each daughter cell is genetically distinct from the others and from the parent cell. Each have a haploid set of unreplicated chromosomes.
53
What are the sister chromatids held together by after interphase?
By proteins called cohesins. The nonsister chromatids are broken at precisely matching points.
54
What is the synaptonemal complex?
A zipper like structure that holds the homologs together tightly.
55
What happens during synapsis?
DNA breaks are repaired, joining DNA from one nonsister chromatid to the corresponding segment of another.
56
What is the comparison between mitosis meiosis?
Mitosis conserves the number of chromosome sets, producing two cells that are genetically identical to the parent cell. Meiosis reduces the number of chromosomes sets from two (diploid) to one (haploid), producing four cells that differ genetically from each other and from the parent cell.
57
What three events are unique to meiosis?
1. Synapsis and crossing over in prophase I: Homologous chromosomes physically connect and exchange genetic information. 2. Alignment of homologous pairs at the metaphase plate. 3. Separation of homologs during anaphase I.
58
What happens to the cohesins during meiosis?
Sister chromatid cohesion allows sister chromatids to stay together through meiosis I. In mitosis, cohesins are cleaved at the end of metaphase, but in meiosis cohesins are cleaved along the chromosome arms in anaphase I (separation of homologs) and at the centromeres in anaphase II (separation of sister chromatids.
59
What is important about mutations?
They are the original source of genetic diversity. Mutations create different versions of genes called alleles. Reshuffling of alleles during sexual reproduction produces genetic variation.
60
What is responsible for most of the variation that arises in each generation?
The behavior of chromosomes during meiosis and fertilization.
61
What mechanisms contribute to genetic variation?
Independent assortment of chromosomes, crossing over, and random fertilization.
62
How do homologous pairs of chromosomes orient themselves at metaphase I?
Randomly. In independent assortment, each pair of chromosomes sorts maternal and paternal homologs into daughter cells independently of the other pairs.
63
What are the possible combinations possible when chromosomes assort independently into gametes?
2n, where n is the haploid number. For humans, n = 23, and there are more than 8 million (2^23) possible combinations of chromosomes.
64
What are recombinant chromosomes?
Crossing over that combines DNA inherited from each parent. Crossing over contributes to genetic variation by combining DNA from two parents into a single chromosome. In humans, an average of one to three crossover events occur per chromosome.
65
What is random fertilization?
Adds to the genetic variation because any sperm can fuse with any ovum (unfertilized egg). The fusion of two gametes (each with 8.4 million possible chromosome combinations from independent assortment) produces a zygote with any of about 70 trillion diploid combinations.
66
How does natural selection happen?
The accumulation of genetic variations favored by the environment, and mutations are the original source of different alleles that are mixed and matched during meiosis.
67
What is the bdelloid rotifer?
An asexually reproducing organism that increases genetic diversity by incorporating foreign DNA from the environment.
68
Is sexual reproduction universal?
Almost, among animals. Prokaryotes do not always sexually reproduce.
69
What is the difference between sister chromatids and homologous chromosomes?
Homologous chromosomes contain the same gene loci, but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication. TLDR: One homologous chromosome comes from the father, and the other comes from the mother. Sister chromatids are identical copies of each other.

General Bio 1 for science majors (11 decks)

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