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Chapter 13 Flashcards

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1
Q

What is the transmission of traits from one generation to the next called?

A

Inheritance or heredity

Inheritance refers to how traits are passed down from parents to offspring.

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2
Q

Are sons and daughters identical copies of either parent?

A

No

Offspring exhibit both inherited similarity and variation.

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3
Q

What is the study of heredity and inherited variation called?

A

Genetics

Genetics involves understanding how traits are passed and vary among individuals.

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4
Q

What are the units of heredity made up of segments of DNA?

A

Genes

Genes are essential for inheritance and determine various traits.

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5
Q

How are genes passed to the next generation?

A

Via reproductive cells called gametes (sperm and eggs)

Gametes are crucial for sexual reproduction, carrying genetic information.

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6
Q

What are the cells called that make up the body except gametes and their precursors?

A

Somatic cells

Somatic cells contain the full set of chromosomes, unlike gametes.

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7
Q

How many chromosomes do humans have in their somatic cells?

A

46 chromosomes

This includes 23 pairs, one from each parent.

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8
Q

What is a gene’s specific position along a chromosome called?

A

Locus

The locus is crucial for identifying where a gene is located on a chromosome.

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9
Q

Fill in the blank: Most DNA is packaged into _______.

A

Chromosomes

Chromosomes organize and protect DNA within the cell.

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10
Q

What is the chromosome number for germ cells?

A

2n

Germ cells undergo meiosis to produce gametes, which have a halved chromosome number.

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11
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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12
Q

What is a clone?

A

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

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13
Q

What characterizes sexual reproduction?

A

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

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14
Q

How many pairs of chromosomes do human somatic cells have?

A

23 pairs of chromosomes.

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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 homologous chromosomes?

A

The two chromosomes in each pair.

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17
Q

What characteristics do chromosomes in a homologous pair share?

A

Same length, centromere position, and staining pattern.

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18
Q

What do homologous chromosomes carry?

A

Genes controlling the same inherited characters.

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19
Q

Fill in the blank: A karyotype is a display of ______.

A

ALL pairs of chromosomes.

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20
Q

True or False: Asexual reproduction results in offspring with unique genetic combinations.

A

False

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21
Q

True or False: Homologous chromosomes have different lengths.

A

False

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22
Q

What are the sex chromosomes that determine the sex of an individual?

A

X and Y

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23
Q

What chromosome pair do human females have?

A

XX

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24
Q

What chromosome pair do human males have?

A

XY

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25
What are the remaining 22 pairs of chromosomes called?
autosomes
26
How many pairs of chromosomes are there in total in a human somatic cell?
23 pairs
27
From whom does each pair of homologous chromosomes come?
one chromosome from each parent
28
How many chromosomes are there in a human somatic cell?
46 chromosomes
29
What is the diploid number for humans?
46 (2n = 46)
30
What type of cell has two sets of chromosomes?
diploid cell (2n)
31
What occurs in a cell after DNA synthesis?
Each chromosome is replicated ## Footnote This results in two identical sister chromatids per chromosome.
32
What does each replicated chromosome consist of?
Two identical sister chromatids ## Footnote Sister chromatids are the result of DNA replication.
33
What is a gamete?
A sperm or egg cell containing a single set of chromosomes ## Footnote Gametes are haploid cells.
34
What is the haploid number for humans?
23 (n = 23) ## Footnote This includes 22 autosomes and one sex chromosome.
35
How many autosomes are in a human haploid cell?
22 autosomes ## Footnote Plus one sex chromosome.
36
What is the sex chromosome in an unfertilized egg (ovum)?
X ## Footnote The ovum contributes an X chromosome to the offspring.
37
What are the possible sex chromosomes in a sperm cell?
X or Y ## Footnote The type of sex chromosome determines the sex of the offspring.
38
What do sister chromatids represent?
Identical copies of a duplicated chromosome ## Footnote They are connected at the centromere.
39
How are homologous chromosomes defined?
A pair of chromosomes, one from each parent ## Footnote They contain the same genes but may have different alleles.
40
What is fertilization?
The union of gametes (the sperm and the egg) ## Footnote Fertilization leads to the formation of a zygote.
41
What is a zygote?
The fertilized egg that has one set of chromosomes from each parent ## Footnote A zygote is diploid (2n = 46) in humans.
42
What process does a zygote undergo to produce somatic cells?
Mitosis ## Footnote Mitosis allows the zygote to develop into an adult.
43
What type of cells do ovaries and testes produce?
Haploid gametes ## Footnote Gametes are produced through meiosis.
44
What is the chromosome number in haploid gametes?
23 (n) ## Footnote Haploid cells have one set of chromosomes.
45
What is the chromosome number in diploid cells?
46 (2n) ## Footnote Diploid cells contain two sets of chromosomes.
46
What type of cell division results in gametes?
Meiosis ## Footnote Gametes are the only type of human cells produced by meiosis.
47
How many sets of chromosomes are in each gamete?
One set ## Footnote Each gamete contains a haploid number of chromosomes.
48
What alternates in sexual life cycles to maintain chromosome number?
Fertilization and meiosis ## Footnote This alternation is crucial for the stability of chromosome numbers across generations.
49
Fill in the blank: Gametes are produced by _______ rather than by mitosis.
meiosis ## Footnote This distinguishes gametes from other human cells.
50
What is the significance of meiosis in human reproduction?
It produces haploid gametes necessary for fertilization ## Footnote This process ensures genetic diversity and correct chromosome numbers.
51
True or False: The zygote is a haploid cell.
False ## Footnote The zygote is diploid, containing two sets of chromosomes.
52
What are gametes?
The only haploid cells in most animals ## Footnote Gametes are produced by meiosis and do not undergo further cell division before fertilization.
53
How are gametes produced?
By meiosis ## Footnote Gametes undergo no further cell division before fertilization.
54
What do gametes fuse to form?
A diploid zygote ## Footnote The zygote divides by mitosis to develop into a multicellular organism.
55
What is the main purpose of meiosis?
To reduce the number of chromosome sets from diploid to haploid
56
What precedes meiosis?
The replication of chromosomes
57
How many cell divisions occur during meiosis?
Two consecutive cell divisions: meiosis I and meiosis II
58
How many daughter cells are produced after meiosis?
Four daughter cells ## Footnote This is in contrast to the two daughter cells produced in mitosis.
59
What is the chromosome number in each daughter cell after meiosis?
Half as many chromosomes as the parent cell
60
What type of cells are produced at the end of meiosis?
Haploid cells with unduplicated chromosomes
61
True or False: Meiosis results in diploid daughter cells.
False ## Footnote Meiosis produces haploid daughter cells.
62
What occurs before meiosis?
Chromosomes duplicate ## Footnote This duplication is essential for the subsequent stages of meiosis.
63
What are sister chromatids?
Duplicated chromosomes associated along their lengths ## Footnote They are connected through sister chromatid cohesion.
64
What is sister chromatid cohesion?
The close association of sister chromatids along their lengths ## Footnote This process is vital for proper chromosome segregation during meiosis.
65
What is the result of meiosis?
Four haploid daughter cells ## Footnote This reduction in chromosome number is crucial for sexual reproduction.
66
How does the chromosome number change during meiosis?
From 2n to n ## Footnote This indicates the reduction from diploid to haploid cells.
67
What are the four phases of meiosis I?
* Prophase I * Metaphase I * Anaphase I * Telophase I and cytokinesis ## Footnote Each phase has distinct events that contribute to genetic diversity and cell division.
68
What happens during early prophase I?
Each chromosome pairs with its homolog and crossing over occurs ## Footnote This is a crucial step for genetic recombination.
69
What are chiasmata?
X-shaped regions that are sites of crossovers ## Footnote Chiasmata are essential for the exchange of genetic material between homologous chromosomes.
70
What happens to chromosomes during metaphase I?
Pairs of homologs line up at the metaphase plate, with one chromosome facing each pole ## Footnote Microtubules from one pole attach to the kinetochore of one chromosome of each pair.
71
What is the role of microtubules during metaphase I?
Microtubules from one pole are attached to the kinetochore of one chromosome, and microtubules from the other pole are attached to the kinetochore of the other chromosome ## Footnote This ensures proper alignment and separation during cell division.
72
What occurs during anaphase I?
Pairs of homologous chromosomes separate, with one chromosome of each pair moving toward opposite poles ## Footnote Sister chromatids remain attached at the centromere and move as one unit.
73
What guides the movement of chromosomes during anaphase I?
The spindle apparatus guides the movement of chromosomes toward opposite poles ## Footnote This mechanism is crucial for the proper segregation of chromosomes.
74
What is the state of the cell at the beginning of telophase I?
Each half of the cell has a haploid set of duplicated chromosomes ## Footnote Each chromosome still consists of two sister chromatids.
75
What occurs simultaneously with telophase I?
Cytokinesis usually occurs simultaneously, forming two haploid daughter cells ## Footnote This completes the first meiotic division.
76
What forms in animal cells during cytokinesis?
A cleavage furrow forms ## Footnote This is the indentation that appears in the cell membrane as the cell divides.
77
What forms in plant cells during cytokinesis?
A cell plate forms ## Footnote This structure develops in the middle of the cell and eventually becomes the new cell wall.
78
Does chromosome replication occur between meiosis I and meiosis II?
No, chromosome replication does not occur ## Footnote The chromosomes are already replicated at the end of meiosis I.
79
What are the four phases of meiosis II?
* Prophase II * Metaphase II * Anaphase II * Telophase II and cytokinesis ## Footnote These phases are similar to those in mitosis.
80
How is meiosis II similar to mitosis?
Meiosis II is very similar to mitosis ## Footnote Both processes involve the separation of sister chromatids.
81
What remains together during Anaphase I?
Sister chromatids remain together ## Footnote This distinguishes Anaphase I from Anaphase II.
82
What is the primary function of meiosis I?
Separates homologous chromosomes ## Footnote This is crucial for reducing the chromosome number in gametes.
83
What is a chiasma in the context of meiosis?
A point where homologous chromosomes exchange genetic material ## Footnote This process increases genetic diversity.
84
Fill in the blank: No _______ occurs between the end of meiosis I and the beginning of meiosis II.
chromosome replication
85
What forms during prophase II?
A spindle apparatus forms ## Footnote This is essential for chromosome movement.
86
What happens to chromosomes during late prophase II?
Chromosomes move toward the metaphase plate ## Footnote Each chromosome is still composed of two chromatids.
87
How are sister chromatids arranged in metaphase II?
Sister chromatids are arranged at the metaphase plate ## Footnote This arrangement is crucial for proper separation.
88
True or False: The sister chromatids of each chromosome are genetically identical in metaphase II.
False ## Footnote This is due to crossing over in meiosis I.
89
What attaches to microtubules in metaphase II?
The kinetochores of sister chromatids ## Footnote They attach to microtubules extending from opposite poles.
90
What occurs during anaphase II?
The sister chromatids separate ## Footnote They move as two newly individual chromosomes toward opposite poles.
91
Fill in the blank: In prophase II, chromosomes are still composed of _______.
[two chromatids]
92
What happens to the sister chromatids during anaphase II?
They move as two newly individual chromosomes toward opposite poles ## Footnote This marks the transition to the next phase of meiosis.
93
What happens to chromosomes during telophase II?
The chromosomes arrive at opposite poles ## Footnote This marks a critical stage in meiosis where chromosomes are separated to opposite ends of the cell.
94
What forms at the end of telophase II?
Nuclei form and chromosomes begin decondensing ## Footnote This process prepares the genetic material for the next stages of cell division.
95
What is the role of cytokinesis in meiosis?
Cytokinesis separates the cytoplasm ## Footnote This is essential for the physical division of the cell into daughter cells.
96
How many daughter cells are produced at the end of meiosis?
Four daughter cells ## Footnote Each of these cells contains a haploid set of unreplicated chromosomes.
97
What is the genetic relationship between daughter cells and the parent cell?
Each daughter cell is genetically distinct from the others and from the parent cell ## Footnote This genetic diversity is a key outcome of meiosis.
98
What type of chromosomes are present in the daughter cells at the end of meiosis?
Haploid set of unreplicated chromosomes ## Footnote Haploid means that each daughter cell contains one set of chromosomes, half the genetic material of the original cell.
99
Fill in the blank: In meiosis II, sister _______ are separated.
chromatids ## Footnote This separation is crucial for ensuring that each daughter cell receives the correct number of chromosomes.
100
What are sister chromatids held together by?
Cohesins ## Footnote Cohesins are proteins that maintain the connection between sister chromatids after interphase.
101
What happens to nonsister chromatids during meiosis?
They are broken at precisely matching points ## Footnote This process is crucial for genetic recombination.
102
What structure holds homologs together tightly during prophase I?
Synaptonemal complex ## Footnote The synaptonemal complex is a zipper-like structure that facilitates the pairing of homologous chromosomes.
103
What is the process called when DNA breaks are repaired and joined from one nonsister chromatid to another?
Synapsis ## Footnote Synapsis occurs during prophase I and is essential for genetic diversity.
104
What is the term for the location where nonsister chromatids exchange genetic material?
Chiasma ## Footnote Chiasma is the point where chromatids cross over and exchange segments.
105
Fill in the blank: After interphase, the sister chromatids are held together by _______.
cohesins
106
True or False: The synaptonemal complex is involved in holding homologs together during prophase I.
True
107
During which phase of meiosis does synapsis occur?
Prophase I ## Footnote This phase is critical for the pairing and recombination of homologous chromosomes.
108
What does mitosis conserve?
The number of chromosome sets ## Footnote Mitosis produces two cells that are genetically identical to the parent cell.
109
What is the result of meiosis?
Four cells that differ genetically from each other and from the parent cell ## Footnote Meiosis reduces the number of chromosomes sets from two (diploid) to one (haploid).
110
How many cells are produced in mitosis?
Two cells ## Footnote Each cell is genetically identical to the parent cell.
111
How many cells are produced in meiosis?
Four cells ## Footnote These cells are genetically different from each other and from the parent cell.
112
What are the three unique events that occur in meiosis I?
1. Synapsis and crossing over in prophase I 2. Alignment of homologous pairs at the metaphase plate 3. Separation of homologs during anaphase I
113
What occurs during synapsis in prophase I of meiosis?
Homologous chromosomes physically connect and exchange genetic information
114
What happens during metaphase I of meiosis?
Homologous pairs align at the metaphase plate
115
What is separated during anaphase I of meiosis?
Homologous chromosomes
116
True or False: Mitosis results in genetically diverse cells.
False ## Footnote Mitosis produces genetically identical cells.
117
Fill in the blank: Meiosis reduces the number of chromosome sets from ______ to one.
two (diploid)
118
Fill in the blank: Mitosis produces ______ cells that are genetically identical.
two
119
Fill in the blank: In meiosis, four cells are produced that are ______ from each other.
genetically different
120
What does mitosis conserve?
The number of chromosome sets ## Footnote Mitosis produces two cells that are genetically identical to the parent cell.
121
What is the result of meiosis?
Four cells that differ genetically from each other and from the parent cell ## Footnote Meiosis reduces the number of chromosomes sets from two (diploid) to one (haploid).
122
How many cells are produced in mitosis?
Two cells ## Footnote Each cell is genetically identical to the parent cell.
123
How many cells are produced in meiosis?
Four cells ## Footnote These cells are genetically different from each other and from the parent cell.
124
What are the three unique events that occur in meiosis I?
1. Synapsis and crossing over in prophase I 2. Alignment of homologous pairs at the metaphase plate 3. Separation of homologs during anaphase I
125
What occurs during synapsis in prophase I of meiosis?
Homologous chromosomes physically connect and exchange genetic information
126
What happens during metaphase I of meiosis?
Homologous pairs align at the metaphase plate
127
What is separated during anaphase I of meiosis?
Homologous chromosomes
128
True or False: Mitosis results in genetically diverse cells.
False ## Footnote Mitosis produces genetically identical cells.
129
Fill in the blank: Meiosis reduces the number of chromosome sets from ______ to one.
two (diploid)
130
Fill in the blank: Mitosis produces ______ cells that are genetically identical.
two
131
Fill in the blank: In meiosis, four cells are produced that are ______ from each other.
genetically different
132
What allows sister chromatids to stay together through meiosis I?
Sister chromatid cohesion ## Footnote Cohesins play a crucial role in maintaining the attachment of sister chromatids during meiosis.
133
When are cohesins cleaved in mitosis?
At the end of metaphase ## Footnote This process allows for the separation of sister chromatids during anaphase.
134
In meiosis, when are cohesins cleaved along the chromosome arms?
In anaphase I ## Footnote This cleavage occurs during the separation of homologs.
135
In meiosis, when are cohesins cleaved at the centromeres?
In anaphase II ## Footnote This cleavage occurs during the separation of sister chromatids.
136
What is the original source of genetic diversity?
Mutations ## Footnote Mutations are changes in an organism's DNA that create different versions of genes.
137
What are different versions of genes called?
Alleles ## Footnote Alleles arise from mutations in the DNA.
138
What contributes to genetic variation during sexual reproduction?
Reshuffling of alleles ## Footnote This process occurs during the formation of gametes and fertilization.
139
What is responsible for most of the variation that arises in each generation?
The behavior of chromosomes during meiosis and fertilization ## Footnote This behavior includes the arrangement and distribution of chromosomes.
140
What are the three mechanisms that contribute to genetic variation?
1. Independent assortment of chromosomes 2. Crossing over 3. Random fertilization ## Footnote Each mechanism plays a vital role in creating genetic diversity among offspring.
141
What happens to homologous pairs of chromosomes at metaphase I of meiosis?
They orient randomly
142
What does independent assortment of chromosomes mean?
Each pair of chromosomes sorts maternal and paternal homologs into daughter cells independently of the other pairs
143
What is the formula for the number of combinations possible when chromosomes assort independently into gametes?
2^n, where n is the haploid number
144
For humans, what is the haploid number (n) of chromosomes?
23
145
How many possible combinations of chromosomes are there for humans due to independent assortment?
More than 8 million (2^23)
146
True or False: Independent assortment means that the arrangement of one pair of chromosomes affects the arrangement of another pair.
False
147
Fill in the blank: The number of combinations possible during independent assortment is represented by _______.
2^n
148
What is the significance of the random orientation of homologous pairs at metaphase I?
It leads to genetic variation in gametes
149
What does crossing over produce?
Recombinant chromosomes ## Footnote Recombinant chromosomes combine DNA inherited from each parent.
150
How does crossing over contribute to genetic variation?
By combining DNA from two parents into a single chromosome
151
In humans, how many crossover events occur on average per chromosome?
One to three
152
Fill in the blank: Crossing over produces _______.
recombinant chromosomes
153
True or False: Crossing over only occurs in one specific chromosome.
False
154
What process adds to genetic variation by allowing any sperm to fuse with any ovum?
Random fertilization ## Footnote Random fertilization contributes significantly to the genetic diversity of offspring.
155
How many possible chromosome combinations can each gamete have from independent assortment?
8.4 million ## Footnote This number arises from the combinations of chromosomes during meiosis.
156
What is the total number of diploid combinations possible when two gametes fuse?
About 70 trillion ## Footnote This vast number results from the combination of the genetic material from both parents.
157
What process contributes additional genetic variation during the formation of gametes?
Crossing over ## Footnote Crossing over occurs during meiosis and results in the exchange of genetic material between homologous chromosomes.
158
What unique genetic identity is formed when two gametes fuse?
Zygote ## Footnote A zygote is the initial cell formed when two gametes merge.
159
Fill in the blank: The fusion of two gametes produces a zygote with any of about _______ diploid combinations.
70 trillion
160
True or False: Each zygote has a unique genetic identity.
True ## Footnote This uniqueness arises from the combination of genetic contributions from both parents.

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