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MCAT Biology > Chapter 2: Reproduction > Flashcards

Chapter 2: Reproduction Flashcards

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1
Q

Diploid

A
  • 2n
  • 2 copies of each chromosome
  • Autosomal cells
  • Humans: 46 (diploid #)
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2
Q

Haploid

A
  • n
  • 1 copy of each chromosome
  • Germ cells
  • Humans: 23 (haploid #)
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3
Q

Stages of Cell Cycle

A
  1. G1 Phase
  2. S Phase
  3. G2 Phase
  4. Mitosis
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4
Q

Interphase

A
  • Consists of G1, S, and G2 phases.
  • Longest part of the cell cycle
  • Less condensed form of DNA
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5
Q

G0 Stage

A
  • Offshoot of G1 stage.
  • Stage where cells that do not divide remain in.
  • Cell is living and serving its function
  • Does NOT prepare for division
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6
Q

Characteristics of chromosomes during interphase

A
  • Less condensed (euchromatin)
  • Enzymes needs to access DNA during transcription and replication.
  • Not visible under light microscopy
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7
Q

Characteristics of chromosomes during mitosis

A
  • More condensed tightly coiled chromosomes (heterochromatin)
  • > More condensed, avoids losing DNA during cell division
  • Visible under light microscopy
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8
Q

G1 Stage

A
  • Cells create organelles for energy and protein production.
  • Increases in cell size
  • Restriction pt after this phase: ensures complement of DNA before proceeding into S phase
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9
Q

S Stage

A
  • Cell replicates genetic material
  • 2 sister chromatids bound together
  • No change in ploidy
  • # of chromatids have doubled
  • Humans: 46 chromosome, 92 chromatids
  • End of S stage results in 2X DNA as cells in G1
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10
Q

Centromere

A

Specialized region where chromatids are bound together.

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11
Q

G2 Stage

A
  • Quality control checkpoint
  • Cells ensure that there are enough organelles and cytoplasm to divide between 2 daughter cells
  • Cells check to make sure DNA replication occurred correctly to avoid passing on error to daughter cells.
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12
Q

Mitosis or M Stage

A
  • Consists of mitosis and cytokinesis
  • Process by which 2 identical daughter cells are created from a single cell.
  • Occurs in somatic cells and autosomal cells.
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13
Q

Phases of Mitosis

A
  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase and Cytokinesis
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14
Q

What are the 2 check points of the cell cycle?

A

1) G1/S Checkpoint

2) G2/M Checkpoint

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15
Q

G1/S Checkpt.

A
  • Also known as restriction pt.
  • Cell determines if DNA is in good enough condition for synthesis
  • If DNA is damaged then cell cycle goes into arrest until DNA is repaired
  • Protein involved is p53.
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16
Q

G2/M Checkpt.

A
  • Ensures cell has achieved proper size and replicated organelles correctly.
  • Protein involved is p53.
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17
Q

p53

A

Protein that plays a role in checkpoints of cell cycle.

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18
Q

Cyclins

A

Molecules responsible for cell cycle.

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19
Q

Cyclin-Dependent Kinases (CDK)

A

Molecules responsible for cell cycle.

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20
Q

Process of Cyclins and CDKs

A
  • CDK needs right cyclins to be activated.
    1. Cyclins bind CDK
    2. Forms activated CDK-cyclin complex
    3. The complex phosphorylates Transcription Factors (TFs)

*Concentrations of cyclins increase or decrease during specific stages.

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21
Q

Transcription Factors

A

Promotes transcription of genes required for the next stage of the cell cycle.

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22
Q

Cancer

A

Abnormal cell cycle control that allows damaged cells to undergo mitosis.

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23
Q

Tumor

A

Cancer cells undergo rapid cell division and form masses

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24
Q

Metastasis

A

Distant spread of cancerous cells through the bloodstream or lymphatic system

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25
Q

Somatic cells

A

Cells that are not involved in sexual reproduction.

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26
Q

Chromatid

A

Composed of a complete double-stranded molecule of DNA.

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27
Q

Sister Chromatids

A

Identical chromatids

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28
Q

Chromosome

A

Can be single chromatid before S phase
OR
Can be pair of chromatids attached at the centromere after S phase

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29
Q

Prophase

A
  • Chromatin condenses into chromosomes
  • Centrioles move to opposite poles of the cells
  • Once at opposite ends of poles, spindle fibers form.
  • Nuclear membrane dissolves, allowing spindle fibers to contact the chromosomes
  • Kinetochores appear at the centromere
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30
Q

Centrosome

A
  • Region in cell where centrioles are located

* One of the microtubule organizing centers (MTOC)

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31
Q

Spindle fibers

A

Composed of microtubules

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32
Q

Centrioles

A

Responsible for correct division of DNA

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33
Q

What are the 2 microtubule organizing centers (MTOC)?

A
  1. Centrosome

2. Basal body of a flagellum or cilium

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34
Q

Asters

A
  • Formed by microtubules

* Anchors the centrioles to the cell membrane

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35
Q

Kinetochore fibers

A

Spindle fibers that extend from kinetochores and interact with spindle fibers from centrioles.

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36
Q

Kinetochores

A

Protein structures located on centromeres that serve as attachment points

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37
Q

Metaphase

A
  • Kinetochore fibers interact with fibers of spindle apparatus from centrioles.
  • Chromosomes pulled to align at metaphase/equatorial plate
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38
Q

Metaphase/Equatorial Plate

A

Equidistant between the 2 poles of the cell.

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39
Q

Anaphase

A
  • Centromeres split
  • Sister chromtids separate
  • Sister chromatids pulled toward opposite poles by shortening of kinetochore fibers.
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40
Q

Telophase

A
  • Is the reverse of prophase
  • Spindle apparatus disappears
  • Nuclear membrane reforms around each set of chromosomes
  • Nucleoli reappears
  • Chromosomes uncoil
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41
Q

Cytokinesis

A
  • Splitting of cytoplasm and organelles into 2 daughter cells.
  • Each daughter cell has sufficient supplies to survive on its own.
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42
Q

Are cell divisions infinite of finite?

A
  • Cell divisions are finite.
  • After x-amount of cell divisions, apoptosis occurs.

*Average # of cell divisions in humans: 20-50

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43
Q

Meiosis

A
  • Occurs in germ cells (gametocytes)

* Results in 4 NONIDENTICAL sex cells (gametes)

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44
Q

Differences between Mitosis and Meiosis

A

Mitosis

  • 1 round of replication + 1 round of division
  • Occurs in somatic cells
  • Results in 2 IDENTICAL diploid daughter cells

Meiosis

  • 1 round of replication + 2 rounds of division
  • Occurs in germ cells
  • Results in 4 NONIDENTICAL haploid cells.
  • Crossing over occurs
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45
Q

Parts of Meiosis

A

Meiosis I and Meiosis II

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46
Q

Meiosis I

A

Reductional Division (2n -> n)

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47
Q

Meiosis II

A

Similar to mitosis

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48
Q

Part of Meiosis I

A 
Prophase I (2n)
Metaphase I (2n)
Anaphase I (2n)
Telophase I (2n)
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49
Q

Parts of Meiosis II

A 
Prophase II (n)
Metaphase II (n)
Anaphase II (n)
Telophase II (n)
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50
Q

How many chromatids, chromosomes, and homologous chromosome pairs are there at the beginning of Meiosis I?

A

92 chromatids
46 chromosomes
23 homologous chromosome pairs

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51
Q

Homologous chromosome pairs

A

Each chromosome is inherited from each parent

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52
Q

Prophase I

A
  • Chromatin condenses into chromosomes
  • Spindle apparatus forms
  • Nucleoli and nuclear membrane disappear
  • Synapsis and crossing over occurs
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53
Q

Synapsis

A

Process in which homologous chromosomes come together and intertwine. Forms a tetrad.

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54
Q

Tetrad

A

Homologous chromosomes held together by synaptonemal complex proteins.

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55
Q

Synaptonemal complex

A

Group of proteins that hold together homologous chromosomes at chiasma

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56
Q

Chiasma

A
  • Point of contact for homologous chromosomes during synapsis.
  • Chromatids of homologous chromosomes may break at this point.
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57
Q

Crossing Over

A

Chromatids of homologous chromosomes break at chiasma and exchange equivalent pieces of DNA.

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58
Q

Genetic Recombination

A
  • Can unlink linked genes

* Increases variety of genetic combinations

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59
Q

Gene Linkage

A

Tendency for genes to be inherited together.

60
Q

Genes located closer together?

A

More likely for gene linkage to occur

61
Q

Genes located farther away from each other?

A

More likely for crossing over to occur and genetic recombination to occur.

62
Q

What type of crossovers are there?

A

Single Crossover

Double Crossover

63
Q

What advantage does sexual reproduction have?

A
  • Provides genetic diversity

- Increases ability of a species to evolve and adapt to a changing environment

64
Q

Allele

A

Variants or alternative forms of genes

65
Q

Mendel’s Second Law

A

Law of Independent Assortment

-Inheritance of one allele has no effect on the likelihood of inheriting certain alleles for other genes.

66
Q

Metaphase I

A

-Homologous chromosome pair (tetrad) align at the metaphase plate via the use of spindle fibers.

67
Q

How many spindle fibers attach to the kinetochore of the homologous chromosome during Metaphase I of meisois?

A

One spindle fiber attaches to the homologous chromosome.

68
Q

How many spindle fibers attach to sister chromatids during Metaphase of mitosis?

A

Two spindle fibers attach to each chromosome.

69
Q

Mendel’s First Law

A

Law of Segregation

-Distribution of homologous chromosomes to daughter cells is random

70
Q

Anaphase I

A

-Disjunction of homologous chromosomes pairs occur.

71
Q

Disjunction

A
  • When homologous chromosome pairs separate and are pulled to opposite poles of the cell.
  • Each chromosome of paternal origin separates (disjoins) from its homologue of maternal origin. Either chromosome can end up in either daughter cell.
72
Q

Telophase I

A
  • Nuclear membrane forms around each new nucleus
  • Cells go from diploid -> haploid
  • Cell divides into 2 daughter cells by cytokinesis.
73
Q

Interkinesis

A
  • Short rest period between cell divisions that may occur.

- During this period, chromosomes partially uncoil.

74
Q

Meiosis II

A
  • Similar to mitosis

- Separation of sister chromatids

75
Q

Prophase II

A
  • Nuclear envelope dissolves
  • Nucleoli disappear
  • Centrioles move to opposite poles of the cell
  • Spindle apparatus begins to form
76
Q

Metaphase II

A

Chromosomes align along the metaphase plate

77
Q

Anaphase II

A
  • The centromeres divide, separating the chromosomes into sister chromatids
  • Chromatids are pulled to opposite poles by spindle fibers
78
Q

Telophase II

A
  • Nuclear membrane forms around each new nucleus
  • Cytokinesis follows and 2 new daughter cells form
  • Results in UP TO 4 haploid daughter cells
79
Q

During what reproductive process does ploidy of resulting cells change?

A

Meiosis

80
Q

In what cells does mitosis occur?

A

Somatic cells

81
Q

In what cells does meiosis occur?

A

Germ cells

82
Q

Do homologous chromosomes pair in mitosis or meiosis?

A

Meiosis

83
Q

Does crossing over occur in mitosis and meiosis?

A

Meiosis

84
Q

What determines biological sex?

A

The 23rd chromosome pair determines biological sex.

XX : Female
XY : Male

85
Q

X chromosome

A

Carries a sizeable amount of genetic information

86
Q

Sex-linked disorders

A

Results from mutations in X chromosome

87
Q

Hemizygous

A

Only one copy of gene present.

Males (XY) are hemizygous

88
Q

What is the pattern of inheritance for most X-linked disorders?

A

Recessively inherited

More frequently expressed in males

89
Q

Carriers

A

Individuals who carry a diseased allele on an X-chromosome, but NOT expressing the disease

90
Q

Y chromosome

A

Contains very little genetic information

91
Q

SRY (Sex-Determining Region Y)

A

Codes for a TF that initiates testis differentiation -> formation of male gonads

92
Q

In the absence of the Y chromosome, what biological sex will the zygote be?

A

Female

93
Q

In the presence of the Y chromosome, what biological sex will the zygote be?

A

Male

94
Q

What are the primtive gonads in males?

A

Testes

95
Q

What are the 2 functional components of the testes?

A
  1. Seminiferous tubules

2. Interstitial cells (of Leydig)

96
Q

Where is sperm produced?

A

Seminiferous tubules

97
Q

Sertoli cells

A

Nourishes sperm cells

98
Q

Interstitial cells of Leydig

A

Secretes testosterone

99
Q

Scrotum

A
  • Location of testes
  • External pouch that hangs below penis
  • Maintains a temperature 2 - 4 deg C lower than the body
100
Q

Pathway of Sperm Through Male Reproductive System

A

Seminiferous Tubules -> Epididymis -> Vas Deferens -> Ejaculatory Duct -> Urethra -> Penis

101
Q

Where does flagella gain motility?

A

Epididymis

102
Q

How many ejaculatory ducts fuse to form the urethra?

A

2

103
Q

In which biological sex is the urinary and reproductive system the same pathway?

A

Males

104
Q

Seminal fluid

A
  • Produced by seminal vesicles, prostate gland, and bulbourethral gland
  • Fluid in which sperm is mixed in with as it passes through the reproductive tract.
105
Q

Seminal vesicles

A

Contributes fructose to nourish sperm and both the seminal vesicles

106
Q

Prostate gland

A

Gives fluid mildly alkaline properties so sperm can survive in the acidic environment of the female reproductive tract

107
Q

Bulbourethral (Cowper’s) gland

A

Produces a clear viscous fluid that cleans out any remnants or urine and lubricates the urethra during sexual arousal

108
Q

Semen

A

Combination of sperm and seminal fluid

109
Q

Spermatogenesis

A

Formation of haploid sperm through meiosis

110
Q

Where does spermatogenesis occur?

A

Seminiferous tubules

111
Q

Spermatogonia

A

Diploid stem cells in males

2n chromosomes

112
Q

Primary spermatocytes

A

Are the products of spermatogonia replicating their genetic material (S stage)

2n chromosomes

113
Q

Secondary spermatocytes

A

Products of the meiosis I of primary spermatocytes

n chromosomes

114
Q

Spermatids

A

Products of meiosis II of secondary spermatocytes

n chromosomes

115
Q

Spermatozoa

A

Spermatids that have undergone maturation

116
Q

How many functional sperm results from spermatogenesis?

A

4

117
Q

Spermatogenesis Sequence

A

Spermatogonia (2n) -> Primary spermatocytes (2n) -> Secondary spermatocytes (n) -> 4 Spermatids (n)
-> 4 Spermatozoa (n)

118
Q

Components of a sperm cell

A
  1. Head
  2. Midpiece
  3. Flagellum
119
Q

Head

A

*Contains genetic material

120
Q

Midpiece

A
  • Generates ATP from fructose

* Filled with mitochondria, which generates the energy to be used as the sperm swims through female reproductive tract

121
Q

Acrosome

A
  • A cap that covers the head of sperm.
  • Derived from Golgi Apparatus
  • Required to penetrate the ovum
122
Q

Flagellum

A

Required for motility

123
Q

What organelle is in the midpiece?

A

Mitochondria

124
Q

What organelle is the acrosome derived from?

A

Golgi Apparatus

125
Q

Are the female reproductive organs external or internal?

A

Internal

126
Q

What are the main gonads in females?

A

Ovaries

127
Q

What hormones are secreted by the ovaries?

A

Estrogen and progesterone

128
Q

What structure does the ovaries contain?

A

It contains thousands of follicles.

129
Q

Follicle

A

Multilayered sacs that contain, nourish, and protect immature ova/eggs

130
Q

How many eggs are ovulated into the peritoneal sac per month between puberty and menopause?

A

1 egg

131
Q

Peritoneal Sac

A

Lines the abdominal cavity

132
Q

Fallopian Tube/Oviduct

A
  • Peritoneal sac leads into it
  • It is lined with cilia, which propels the egg forward
  • Site where fertilization occurs
133
Q

Uterus

A
  • Site where fetal development occurs

* Fallopian tube connects to this muscular structure

134
Q

Cervix

A

Lower end of the uterus

135
Q

Vaginal Canal

A
  • Connects to the cervix
  • Site where sperm is deposited during intercourse
  • Passageway through which childbirth occurs
136
Q

Vulva

A

External female anatomy

137
Q

Pathway for Female Reproductive System

A

Follicles in Ovaries -> Peritoneal Sac -> Fallopian Tube/Oviduct -> Uterus -> Cervix -> Vaginal Canal -> Vulva

138
Q

Oogenesis

A

*Production of female gametes

139
Q

In males, is the spermatogonia stem cells limited or unlimited?

A

There is an unending supply of spermatogonia stem cells.

140
Q

In females, is the oogonia stem cells limited or unlimited?

A
  • There is a limited supply of oogonia.

* All the oogonia a woman will have are formed during fetal development.

141
Q

Oogonia

A

Female reproductive stem cells

2n chromosomes

142
Q

Primary oocytes

A
  • The female reproductive cells at birth that have undergone DNA replication already.
  • Birth -> Menarche
  • Cells arrested in Prophase I

2n chromosomes

143
Q

Secondary oocytes

A

*Cell that results from one primary oocyte completing Meiosis I per month

144
Q

Menarche

A
  • First menstrual cycle

* One primary oocyte completes Meiosis I and produces a secondary oocyte and a polar body

145
Q

How often does the menstrual cycle take place?

A

Once per month

146
Q

Why is the polar body produced and not 2 complete oocytes?

A

It is a result of unequal cytokinesis.

*Secondary oocyte has ample cytoplasm but polar body has very little to none.

MCAT Biology (2 decks)

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