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MCAT Biology > Chapter 2: Reproduction > Flashcards

Chapter 2: Reproduction Flashcards

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1
Q

What is diploid?

A

2 copies of each chromosome

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2
Q

What is haploid?

A

1 copy of each chromosome

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3
Q

Are autosomal cells haploid or diploid?

A

Diploid (2n)

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4
Q

Are germ cells haploid or diploid?

A

Haploid (n)

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5
Q

What are the 4 stages of the cell cycle?

A

G1
S
G2
M

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6
Q

Which of these stages comprise interphase? : G1, S, G2, M

A

G1, S, G2

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7
Q

Interphase is the (longest/shortest) part of the cell cycle. Actively dividing cells spend 90% of their time in interphase.

A

Longest

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8
Q

Cells that do not divide spend all of their time in an offshoot of G1 called ____, where the cell simply lives and carries out its functions, without preparing for division.

A

G0

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9
Q

During interphase, individual chromosomes are in a less condensed form known as ____________.

A

Chromatin

not visible by light microscopy

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10
Q

During mitosis, it is preferable to condense DNA into tightly coiled ________________ to avoid losing any genetic material during cell division.

A

Chromosomes

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11
Q

What occurs during the G1 stage?

A
  1. Cells create organelles for energy and protein production
  2. Cells increase in size
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12
Q

Passage into the S (synthesis) stage is governed by a ______________ ________.

A

Restriction point

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13
Q

What occurs during the S stage?

A

Cell replicates its genetic material so that each daugher cell has identical copies

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14
Q

After replication in the S stage, each chromosome consists of 2 identical ________________ that are bound together at a specialized region known as the ________________.

A

chromatids; centromere

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15
Q

Does the ploidy of cells change after replication in G1?

A

No, it simply has more DNA, but still only has 46 chromosomes.

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16
Q

Cells entering G2 have ________ as much DNA as cells in G1.

A

Twice

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17
Q

During the G2 stage, DNA has been duplicated, and the cell checks to ensure there are enough ________________ and ________________ for 2 daughter cells. It also checks to make sure that DNA replication proceeded correctly.

A

Organelles and cytoplasm

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18
Q

What are the 4 phases of mitosis?

A
  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase
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19
Q

What are the 2 primary checkpoints in the cell cycle?

A

G1/S and G2/M

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20
Q

What does the cell check for at the G1/S checkpoint, i.e. restriction point?

A

If the condition of the DNA is good enough for synthesis

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21
Q

If the DNA is damaged at the G1/S checkpoint, what happens? What protein is in control of this?

A

The cell cycle goes into arrest until the DNA is repaired. p53 is the main protein.

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22
Q

What does the cell check for at the G2/M checkpoint? What protein is involved?

A

If it has achieved adequate size and the organelles have been properly replicated to support 2 daughter cells. p53 is also at play.

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23
Q

Which 2 molecules are responsible for the cell cycle?

A
  1. Cyclins
  2. Cyclin-dependent kinases (CDK)
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24
Q

How are CDKs activated?

A

They require the presence of the right cyclins

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25
Q

During the cell cycle, concentrations of various cyclins increase and decrease. These cyclins bind CDKs, creating an activated _________ - __________ ___________, which can then phosphorylate _______________ _________.

A

CDK-cyclin complex; transcription factors

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26
Q

What is a common mutation of p53 that can cause cancer?

A

TP53

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27
Q

What occurs in TP53 mutation?

A

The cell cycle is not stoppped to repair damaged DNA, allowing mutations to accumulate, resulting in a cancerous cell that divides continuously, creating tumors

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28
Q

List 4 steps

What occurs during prophase?

A
  1. Chromatin condenses into chromosomes
  2. Centrioles separate and migrate to opposite poles
  3. Centrioles begin to form spindle fibers
  4. The nuclear membrane dissolves, allowing these spindle fibers to contact the chromosomes
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29
Q

Centrioles are located outside the nucleus in a region known as the ________________ and are responsible for the correct division of DNA.

A

Centrosome

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30
Q

What are spindle fibers made of ?

A

Microtubules

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31
Q

Since spindle fibers are made of microtubules, the centrosome is one of two ___________________ ______________ _________ of the cell.

A

Microtubule organizing centers

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32
Q

Besides the centrosome, what is the other microtubule organizing centers of the cell?

A

The basal body of a flagellum or cilium

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33
Q

Some microtubules form ________ that anchor the centrioles to the cell membrane.

A

asters

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34
Q

________________, which appear at the centrosome, are protein structures located on the centromeres of chromosomes that serve as attachment points for specific fibers of the ____________ ________________ (kinetochore fibers).

A

Kinetochores; spindle apparatus

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35
Q

2 steps

What happens during metaphase?

A
  1. Centriole pairs are at opposite poles
  2. Kinetochore fibers interact with the fibers of the spindle apparatus to align the chromosomes at the metaphase plate.
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36
Q

2 steps

What happens during anaphase?

A
  1. Centromeres split so that each chromatid has its own distinct centromere
  2. Sister chromatids are pulled toward the opposite poles of the cell by the shortening of kinetochore fibers
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37
Q

4 steps

What occurs during telophase?

A
  1. Spindle apparatus disappears
  2. Nuclear membrane reforms around each set of chromosomes
  3. Nucleoli reappear
  4. Chromosomes uncoil
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38
Q

What is cytokinesis?

A

Separation of cytoplasm and organelles

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39
Q

Meiosis occurs in germ cells and results in up to (how many?) nonidentical sex cells (gametes).

A

4

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40
Q

How many rounds of replication and division does mitosis have?

A

1 round of replication and 1 round of division

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41
Q

How many rounds of replication and division does meiosis have?

A

1 round of replication, 2 rounds of division

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42
Q

Meiosis I results in homologous chromosomes being separated, generating haploid daughter cells; this is known as ____________________ division.

A

Reductional

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43
Q

Meiosis II is most similar to mitosis, in that it results in the separation of sister chromatids without a change in ploidy, and is therefore known as ____________________ division.

A

Equational

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44
Q

What are homologous pairs of chromosomes?

A

Each pair contains 1 chromosome inherited from each parent

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45
Q

In meiosis, after S phase, there are (how many?) chromatids organized into (how many?) chromosomes, which are organized into (how many?) homologous pairs.

A

92, 46, 23

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46
Q

What are the 3 main events in Prophase I?

A
  1. Chromatin condenses into chromosomes
  2. Spindle apparatus forms
  3. Nucleoli and nuclear membrane disappear
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47
Q

During Prophase I, the homologous chromosomes come together and intertwine in a process called _____________.

A

Synapsis

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48
Q

At this point, each chromosome is made up of 2 chromatids, so each synaptic pair contains (how many?) chromatids and is referred to as a _____________.

A

4; tetrad

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49
Q

The homologous chromosomes are held together by a group of proteins called the ____________________ ___________.

A

Synaptonemal complex

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50
Q

Chromatids of homologous chromosomes may break at the point of contact, called the ____________, and exchange equivalent pieces of DNA.

A

Chiasma

plural: chiasmata

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51
Q

What is the process of exchanging chromatids exchanging DNA called?

A

Crossing over

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52
Q

What is crossing over characterized by?

A

The number of crossover events that occur in one strand of DNA

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53
Q

Crossing over can unlink linked genes, thereby increasing the variety of genetic ________________ that can be produced by gametogenesis.

A

Recombination

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54
Q

What is gene linkage?

A

Tendency for genes to be inherited together

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55
Q

Genes that are located farther from each other physically are (more/less) likely to be inherited together, and (more/less) likely to undergo crossing over relative to each other.

A

less; more

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56
Q

What is the unit of measurement for distance between genes on the chromosome?

A

Centimorgans

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57
Q

What does Mendel’s second law of independent assortment state?

Has to do with crossing over

A

The inheritance of one allele has no effect on the likelihood of inheriting certain alleles for other genes

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58
Q

What are the 2 main steps in Metaphase I?

A
  1. Tetrads (homologous pairs) align at the metaphase plate
  2. Each pair attaches to a separate spindle fiber by its kinetochore
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59
Q

What occurs during Anaphase I?

A
  1. Homologous pairs separate and are pulled to opposite poles of the cell

This is disjunction

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60
Q

What is Mendel’s first law of segregation?

A

during gamete formation, the two alleles at a gene locus segregate from each other; each gamete has an equal probability of containing either allele

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61
Q

What occurs during disjunction?

A

Each chromosome of paternal origin separates from its homologous of maternal origin, and eater chromosome can end up in either daughter cell. Thus, the distribution of homologous chromosomes to the 2 intermediate daughter cells is random with respect to parental origin.

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62
Q

What is the separation of 2 homolgous chromosomes called?

A

Segregation

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63
Q

What occurs during Telophase I?

A
  1. A nuclear membrane forms around each new nucleus
  2. The cell divides into 2 daughter cells by cytokinesis
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64
Q

After Telophase I, are the cells haploid or diploid?

A

Haploid

Only n chromosomes are found in each daugher cell (23 in humans)

65
Q

Between cell division, there may be a short rest period, or ________________, during which the chromosomes partially uncoil.

A

Interkinesis

66
Q

What occurs in Meiosis II?

A

Sister chromatids separate from each other

67
Q

4 phases

What occurs during Prophase II?

A
  1. Nuclear envelope dissolves
  2. Nucleoli disappear
  3. Centrioles migrate to opposite poles
  4. Spindle apparatus begins to form
68
Q

What occurs during Metaphase II?

A

Chromosomes line up on metaphase plate

69
Q

What occurs during Anaphase II?

A
  1. Centromeres divide, separating chromosomes into sister chromatids
  2. Chromatids are pulled to opposite poles by spindle fibers
70
Q

What occurs during Telophase II?

A
  1. A nuclear membrane forms around each new nucleus
  2. Cytokinesis follows, and 2 daughter cells are formed per each
71
Q

Which pair of chromosomes determine chromosomal sex?

A

23rd

72
Q

Mutations in the genes of the X chromosome can cause ___-___________ disorders.

aka?

A

sex-linked

X-linked

73
Q

Males are termed ________________ with respect to many of the genes on the X chromosome because they only have one copy.

A

Hemizygous

74
Q

What is one major consequence of males only having one X chromosome?

A

They tend to express X-linked disorders more frequently than females.

75
Q

dominantly or recessively?

Most X-linked disorders are ________________ inherited.

A

recessively

76
Q

The (X or Y?) chromosome contains very little genetic information.

A

Y

77
Q

A notable gene on the Y chromosome is ________, which codes for a transcription factor that initiates testis differentiation and thus, the formation of male gonads.

what does it stand for?

A

SRY

sex-determining region Y

78
Q

What is the pathway of sperm through the male reproductive system?

SEVE(N) UP

A
  1. Seminiferous tubules
  2. Epididymis
  3. Vas deferens (also called ductus deferens)
  4. Ejaculatory duct
  5. (Nothing)
  6. Urethra
  7. Penis
79
Q

In males, the primitive gonads develop into the ________.

A

Testes

80
Q

The testes have 2 functional components, the ________________ tubules and the interstitial cells of ____________.

A

seminiferous; Leydig

81
Q

Where are sperm produced?

A

In the highly coiled seminiferous tubules

82
Q

____________ cells nourish the sperm in the seminiferous tubules.

A

Sertoli

83
Q

The cells of Leydig secrete ________________ and other male sex hormones known as ____________.

A

testosterone; androgens

84
Q

The testes are located in the ____________, an external pouch that hangs below the ________, which allows it to maintain a temperature 2-4 deg C cooler than the body.

A

scrotum; penis

85
Q

The ____ ____________ has a layer of muscle that can raise and lower the testis to maintain the proper temperature for sperm development.

aka?

A

vas deferens

ductus deferens

86
Q

Once sperm are formed in the seminiferous tubules of the testes, they are passed to the ____________________, where their flagella gain motility. They are stored there until ______________.

A

epididymis; ejaculation

87
Q

During ejaculation, sperm travel through the ____ ____________ and enter the ______________ ______ at the posterior edge of the prostate gland.

A

vas deferens; ejaculatory duct

88
Q

The 2 ejaculatory ducts fuse to form the ________, which carries sperm through the penis.

A

urethra

89
Q

As sperm pass through the reproductive tract, they mix with ____________ ________, which is produced by what 3 things?

A

seminal fluid; seminal vesicles, prostate gland, and bulbourethral gland

90
Q

The seminal vesicles contribute ____________ to nourish sperm, and both the seminal vescles and ____________ gland give the fluid mildly alkaline properties so they can survive the relatively acidic female reproductive tract.

A

fructose; prostate

91
Q

The ________________ glands produce a clear viscous fluid that cleans out any remnants of urine and lubricates the urethra during sexual arousal.

aka?

A

bulbourethral

Cowper’s

92
Q

The combination of sperm and seminal fluid is ________.

A

Semen

93
Q

In males, the diploid stem cells are known as _________________.

A

Spermatogonia

94
Q

After spermatogonia replicate their genetic material (S stage), they develop into (diploid or haploid?) ____________ ______________________.

A

diploid primary spermatocytes

95
Q

The first meiotic division of primary spermatocytes results in (diploid or haploid?) __________________ ______________________.

A

haploid secondary spermatocytes

96
Q

Secondary spermatocytes undergo meiosis II to generate (diploid or haploid?) ______________.

A

haploid spermatids

97
Q

The spermatids then undergo maturation to become mature ________________.

A

spermatozoa

98
Q

Spermatogenesis results in (how many?) functional sperm for each spermatogonoium.

A

4

99
Q

What are the 3 main parts of sperm?

A
  1. Head
  2. Midpiece
  3. Flagellum
100
Q

What is contained in the sperm head?

A

Genetic material

101
Q

What is inside the sperm midpiece and what do they generate?

A

Mitochondria generates ATP from fructose for swimming.

102
Q

Each sperm head is covered by a cap known as a ____________. It is necessary to penetrate the ovum.

A

Acrosome

103
Q

The female gonads, known as ____________, produce ____________ and ____________________.

A

ovaries; estrogen and progesterone

104
Q

The ovaries are located in the __________ _________.

A

Pelvic cavity

105
Q

Each ovary consists of thousands of ____________, which are multilayered sacs that contain, nourish, and protect immature ____.

A

follicles; ova

106
Q

One egg per month is ____________ into the ________________ sac, which lines the abdominal cavity.

A

ovulated; peritoneal

107
Q

Upon ovulation, the egg is drawn into the ______________ ______, or ________, which is lined with cilia to propel the egg forward.

A

fallopian tube; oviduct

108
Q

The fallopian tubes are connected to the muscular ________, where the fetus develops.

A

Uterus

109
Q

The lower end of the uterus, known as the ________, connects to the ____________ ________, where sperm are deposited during intercourse.

A

cervix; vaginal canal

110
Q

The production of female gametes is known as ____________.

A

oogenesis

111
Q

By birth, all of a female’s oogonia have already undergone DNA replication and are considered ______________ __________.

A

primary oocytes

112
Q

What is the ploidy of primary oocytes?

A

2n

113
Q

Primary oocytes are arrested in ___________ __.

A

Prophase I

114
Q

After menarche (first menstrual cycle), 1 primary oocyte per month will complete ____________ ____, producing a __________________ __________ and a ________ _______.

A

Meiosis I; secondary oocyte and polar body

115
Q

Meiosis I in oocytes is characterized by unequal ________________. This causes ample cytoplasm to be distributed to 1 daughter cell (secondary oocyte) and nearly none to the other (polar body).

A

cytokinesis

116
Q

What happens to the polar body?

A

It does not divide any further and does not produce functional gametes

117
Q

What happens to the secondary oocyte?

A

It is arrested in metaphase II and does not complete meiosis II until fertilization occurs

118
Q

What are the 2 layers surrounding oocytes?

A

zona pellucida and the corona radiata

119
Q

What is the zona pellucida and what is it made of and what does it do?

A

Surrounds the oocyte itself and is an acellular mixture of glycoproteins that protects the oocyte and contains compounds necessary for sperm cell binding

120
Q

What is the corona radiata?

A

Surrounds the zona pellucida; it is a layer of cells that adheres to the oocyte during ovulation

121
Q

What triggers Meiosis II?

A

When a sperm cell penetrates the zona pellucida and corona radiata with the help of acrosomal enzymes

122
Q

What happens after Meiosis II?

A

The secondary oocyte splits into a mature ovum and another polar body

123
Q

What do the ovum and sperm each contribute to the zygote?

A

Ovum; half of DNA, all of cytoplasm/organelles/RNA

Sperm; half of the DNA

124
Q

After Meiosis II, the (diploid/haploid?) ____________ of the sperm and the ovum join, creating a (diploid/haploid?) ____________.

A

haploid pronuclei; diploid zygote

125
Q

What controls the ability to reproduce?

A

Hormones

126
Q

Prior to puberty, the ________________ restricts production of ____________________-________________ hormone.

A

Hypothalamus; gonadotropin-releasing (GnRH)

127
Q

At the start of puberty, the hypothalamus releases pulses of ________, which triggers the (anterior/posterior?) pituitary gland to synthesize and release _____________-_________________ hormone and ____________________ hormone.

A

GnRH; anterior; follicule-stimulating (FSH); luteinizing (LH)

128
Q

What do FSH and LH do?

A

Trigger the production of other sex hormones

129
Q

During the fetal period (9 weeks post-fertilization till birth), the presence of the Y chromosome in males leads to the production of ________________, which results in male sexual differentiation.

A

androgens

130
Q

For the duration of infancy and childhood, androgen production is (high/low?).

A

Low

131
Q

By puberty, the testes dramatically increase production of ____________________, and sperm production begins.

A

testosterone

132
Q

During puberty, ____ stimulates the Sertoli cells and triggers what?

Whereas ____ causes the interstitial cells to produce what?

A

FSH, sperm maturation; LH, testosterone

133
Q

The ovaries are also under the control of FSH and LH but they produce what instead?

A

Estrogens and progesterone

134
Q

What does FSH stimulate the secretion of in females? What does this stimulate the development of in embroys? In adults?

A

estrogens; female reproductive tract; endometrial lining in preparation for zygote implantation

135
Q

What do estrogen and progesterone do?

Est-est-pro-pro

A

Estrogen establishes and progesterone protects the endometrium.

Estrogen - thickens endomet.
Progesterone - develops/maintains endomet.

136
Q

What is the corpus luteum?

A

The remains of the ovarian follicle following ovulation

137
Q

What does LH stimulate the secretion of in females? From where?

A

Progesterone from corpus luteum

138
Q

What are the 4 events of the menstrual cycle?

A
  1. Follicular phase
  2. Ovulation
  3. Luteal phase
  4. Menstruation
139
Q

What marks the start of the follicular phase?

A

When the menstrual flow begins

uterine lining of previous cycle is shed

140
Q

________ secretion from the hypothalamus increases in response to the decreased concentrations of ____________ and ________________, which fall off towards the end of each cycle.

A

GnRH; estrogen and progesterone

141
Q

The higher concentrations of GnRH cause increased secretion of what in the hypothalamus?

A

FSH and LH

142
Q

What do FSH and LH do in the follicular phase?

A

Develop several ovarian follicles which begin to produce estrogen

143
Q

What do the follicles do in the follicular phase?

A

Produce estrogen, which causes GnRH, LH, and FSH concentrations to level off

negative feedback

144
Q

What does estrogen do in the follicular phase?

A

Stimulates regrowth of the endometrial lining

145
Q

Estrogen stimulates vascularization and glandularization of the ___________.

A

Decidua

thick layer of mucous membrane which lines uterus during pregnancy

146
Q

Late in the follicular phase, the developing follicles secrete higher and higher concentrations of estrogen. This reaches a threshold that results in positive feedback, and GnRH, LH, and FSH levels spike. The surge in LH induces _____________.

A

ovulation

ovary releases ovum into abdominal cavity

147
Q

After ovulation, LH causes the ruptured follicle to form the ________ ________, which secretes _________________.

A

corpus luteum; progesterone

148
Q

During the luteal phase, progesterone levels (rise/fall?), while estrogen levels remain (high/low?).

A

rise; high

149
Q

What do the high levels of progesterone do in the luteal phase?

A

Cause negative feedback on GnRH, FSH, LH, preventing ovulation of multiple eggs

150
Q

If implantation does not occur, the corpus luteum loses its stimulation from LH, progesterone levels (rise/decline?) and the uterine lining is sloughed off.

A

Decline

151
Q

The loss of high levels of estrogen and progesterone do what to GnRH?

A

Remove the block on GnRH, so that the next cycle can begin

152
Q

If fertilization occurs, the zygote develops into a ____________ that will implant in the uterine lining and secrete __________ _____________ ___________________, which is an analog of LH and can stimulate LH receptors to maintain the corpus luteum.

A

blastocyst; human chorionic gonadotropin (hCG)

153
Q

What is hCG important for in the first trimester?

A

Keeping the uterine lining in place by maintaining the corpus luteum (and allowing it to continue secreting estrogen and progesterone)

154
Q

In the second trimester, why do hCG levels decline?

A

The placent has grown large enough to secrete enough progesterone and estrogen by itself

155
Q

What do the high levels of estrogen and progesterone do during pregnancy?

A

Negative feedback on GnRH secretion

156
Q

As we age, the ovaries become (more/less?) sensitive to FSH and LH, resulting in what?

A

Less; ovarian atrophy

157
Q

As estrogen and progesterone levels drop as we age, the endometrium also atrophies, causing what?

A

The stopping of menstruation, aka menopause

158
Q

What happens as a result of the removal of negative feedback on FSH and LH during menopause?

A

FSH and LH blood levels rise

MCAT Biology (12 decks)

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