Chapter 2: Reproduction Flashcards
1
Q
Diploid
A
- 2n
- 2 copies of each chromosome
- Autosomal cells
- Humans: 46 (diploid #)
2
Q
Haploid
A
- n
- 1 copy of each chromosome
- Germ cells
- Humans: 23 (haploid #)
3
Q
Stages of Cell Cycle
A
- G1 Phase
- S Phase
- G2 Phase
- Mitosis
4
Q
Interphase
A
- Consists of G1, S, and G2 phases.
- Longest part of the cell cycle
- Less condensed form of DNA
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
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
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
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
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
10
Q
Centromere
A
Specialized region where chromatids are bound together.
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.
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.
13
Q
Phases of Mitosis
A
- Prophase
- Metaphase
- Anaphase
- Telophase and Cytokinesis
14
Q
What are the 2 check points of the cell cycle?
A
1) G1/S Checkpoint
2) G2/M Checkpoint
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.
16
Q
G2/M Checkpt.
A
- Ensures cell has achieved proper size and replicated organelles correctly.
- Protein involved is p53.
17
Q
p53
A
Protein that plays a role in checkpoints of cell cycle.
18
Q
Cyclins
A
Molecules responsible for cell cycle.
19
Q
Cyclin-Dependent Kinases (CDK)
A
Molecules responsible for cell cycle.
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.
21
Q
Transcription Factors
A
Promotes transcription of genes required for the next stage of the cell cycle.
22
Q
Cancer
A
Abnormal cell cycle control that allows damaged cells to undergo mitosis.
23
Q
Tumor
A
Cancer cells undergo rapid cell division and form masses
24
Q
Metastasis
A
Distant spread of cancerous cells through the bloodstream or lymphatic system
25
Somatic cells
Cells that are not involved in sexual reproduction.
26
Chromatid
Composed of a complete double-stranded molecule of DNA.
27
Sister Chromatids
Identical chromatids
28
Chromosome
Can be single chromatid before S phase
OR
Can be pair of chromatids attached at the centromere after S phase
29
Prophase
* 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
30
Centrosome
* Region in cell where centrioles are located
| * One of the microtubule organizing centers (MTOC)
31
Spindle fibers
Composed of microtubules
32
Centrioles
Responsible for correct division of DNA
33
What are the 2 microtubule organizing centers (MTOC)?
1. Centrosome
| 2. Basal body of a flagellum or cilium
34
Asters
* Formed by microtubules
| * Anchors the centrioles to the cell membrane
35
Kinetochore fibers
Spindle fibers that extend from kinetochores and interact with spindle fibers from centrioles.
36
Kinetochores
Protein structures located on centromeres that serve as attachment points
37
Metaphase
* Kinetochore fibers interact with fibers of spindle apparatus from centrioles.
* Chromosomes pulled to align at metaphase/equatorial plate
38
Metaphase/Equatorial Plate
Equidistant between the 2 poles of the cell.
39
Anaphase
* Centromeres split
* Sister chromtids separate
* Sister chromatids pulled toward opposite poles by shortening of kinetochore fibers.
40
Telophase
* Is the reverse of prophase
* Spindle apparatus disappears
* Nuclear membrane reforms around each set of chromosomes
* Nucleoli reappears
* Chromosomes uncoil
41
Cytokinesis
* Splitting of cytoplasm and organelles into 2 daughter cells.
* Each daughter cell has sufficient supplies to survive on its own.
42
Are cell divisions infinite of finite?
* Cell divisions are finite.
* After x-amount of cell divisions, apoptosis occurs.
*Average # of cell divisions in humans: 20-50
43
Meiosis
* Occurs in germ cells (gametocytes)
| * Results in 4 NONIDENTICAL sex cells (gametes)
44
Differences between Mitosis and Meiosis
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
45
Parts of Meiosis
Meiosis I and Meiosis II
46
Meiosis I
Reductional Division (2n -> n)
47
Meiosis II
Similar to mitosis
48
Part of Meiosis I
```
Prophase I (2n)
Metaphase I (2n)
Anaphase I (2n)
Telophase I (2n)
```
49
Parts of Meiosis II
```
Prophase II (n)
Metaphase II (n)
Anaphase II (n)
Telophase II (n)
```
50
How many chromatids, chromosomes, and homologous chromosome pairs are there at the beginning of Meiosis I?
92 chromatids
46 chromosomes
23 homologous chromosome pairs
51
Homologous chromosome pairs
Each chromosome is inherited from each parent
52
Prophase I
* Chromatin condenses into chromosomes
* Spindle apparatus forms
* Nucleoli and nuclear membrane disappear
* Synapsis and crossing over occurs
53
Synapsis
Process in which homologous chromosomes come together and intertwine. Forms a tetrad.
54
Tetrad
Homologous chromosomes held together by synaptonemal complex proteins.
55
Synaptonemal complex
Group of proteins that hold together homologous chromosomes at chiasma
56
Chiasma
* Point of contact for homologous chromosomes during synapsis.
* Chromatids of homologous chromosomes may break at this point.
57
Crossing Over
Chromatids of homologous chromosomes break at chiasma and exchange equivalent pieces of DNA.
58
Genetic Recombination
* Can unlink linked genes
| * Increases variety of genetic combinations
59
Gene Linkage
Tendency for genes to be inherited together.
60
Genes located closer together?
More likely for gene linkage to occur
61
Genes located farther away from each other?
More likely for crossing over to occur and genetic recombination to occur.
62
What type of crossovers are there?
Single Crossover
| Double Crossover
63
What advantage does sexual reproduction have?
- Provides genetic diversity
| - Increases ability of a species to evolve and adapt to a changing environment
64
Allele
Variants or alternative forms of genes
65
Mendel's Second Law
Law of Independent Assortment
| -Inheritance of one allele has no effect on the likelihood of inheriting certain alleles for other genes.
66
Metaphase I
-Homologous chromosome pair (tetrad) align at the metaphase plate via the use of spindle fibers.
67
How many spindle fibers attach to the kinetochore of the homologous chromosome during Metaphase I of meisois?
One spindle fiber attaches to the homologous chromosome.
68
How many spindle fibers attach to sister chromatids during Metaphase of mitosis?
Two spindle fibers attach to each chromosome.
69
Mendel's First Law
Law of Segregation
| -Distribution of homologous chromosomes to daughter cells is random
70
Anaphase I
-Disjunction of homologous chromosomes pairs occur.
71
Disjunction
- 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
Telophase I
- Nuclear membrane forms around each new nucleus
- Cells go from diploid -> haploid
- Cell divides into 2 daughter cells by cytokinesis.
73
Interkinesis
- Short rest period between cell divisions that may occur.
| - During this period, chromosomes partially uncoil.
74
Meiosis II
- Similar to mitosis
| - Separation of sister chromatids
75
Prophase II
- Nuclear envelope dissolves
- Nucleoli disappear
- Centrioles move to opposite poles of the cell
- Spindle apparatus begins to form
76
Metaphase II
Chromosomes align along the metaphase plate
77
Anaphase II
- The centromeres divide, separating the chromosomes into sister chromatids
- Chromatids are pulled to opposite poles by spindle fibers
78
Telophase II
- Nuclear membrane forms around each new nucleus
- Cytokinesis follows and 2 new daughter cells form
- Results in UP TO 4 haploid daughter cells
79
During what reproductive process does ploidy of resulting cells change?
Meiosis
80
In what cells does mitosis occur?
Somatic cells
81
In what cells does meiosis occur?
Germ cells
82
Do homologous chromosomes pair in mitosis or meiosis?
Meiosis
83
Does crossing over occur in mitosis and meiosis?
Meiosis
84
What determines biological sex?
The 23rd chromosome pair determines biological sex.
XX : Female
XY : Male
85
X chromosome
Carries a sizeable amount of genetic information
86
Sex-linked disorders
Results from mutations in X chromosome
87
Hemizygous
Only one copy of gene present.
| Males (XY) are hemizygous
88
What is the pattern of inheritance for most X-linked disorders?
Recessively inherited
More frequently expressed in males
89
Carriers
Individuals who carry a diseased allele on an X-chromosome, but NOT expressing the disease
90
Y chromosome
Contains very little genetic information
91
SRY (Sex-Determining Region Y)
Codes for a TF that initiates testis differentiation -> formation of male gonads
92
In the absence of the Y chromosome, what biological sex will the zygote be?
Female
93
In the presence of the Y chromosome, what biological sex will the zygote be?
Male
94
What are the primtive gonads in males?
Testes
95
What are the 2 functional components of the testes?
1. Seminiferous tubules
| 2. Interstitial cells (of Leydig)
96
Where is sperm produced?
Seminiferous tubules
97
Sertoli cells
Nourishes sperm cells
98
Interstitial cells of Leydig
Secretes testosterone
99
Scrotum
- Location of testes
- External pouch that hangs below penis
- Maintains a temperature 2 - 4 deg C lower than the body
100
Pathway of Sperm Through Male Reproductive System
Seminiferous Tubules -> Epididymis -> Vas Deferens -> Ejaculatory Duct -> Urethra -> Penis
101
Where does flagella gain motility?
Epididymis
102
How many ejaculatory ducts fuse to form the urethra?
2
103
In which biological sex is the urinary and reproductive system the same pathway?
Males
104
Seminal fluid
- 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
Seminal vesicles
Contributes fructose to nourish sperm and both the seminal vesicles
106
Prostate gland
Gives fluid mildly alkaline properties so sperm can survive in the acidic environment of the female reproductive tract
107
Bulbourethral (Cowper's) gland
Produces a clear viscous fluid that cleans out any remnants or urine and lubricates the urethra during sexual arousal
108
Semen
Combination of sperm and seminal fluid
109
Spermatogenesis
Formation of haploid sperm through meiosis
110
Where does spermatogenesis occur?
Seminiferous tubules
111
Spermatogonia
Diploid stem cells in males
2n chromosomes
112
Primary spermatocytes
Are the products of spermatogonia replicating their genetic material (S stage)
2n chromosomes
113
Secondary spermatocytes
Products of the meiosis I of primary spermatocytes
n chromosomes
114
Spermatids
Products of meiosis II of secondary spermatocytes
n chromosomes
115
Spermatozoa
Spermatids that have undergone maturation
116
How many functional sperm results from spermatogenesis?
4
117
Spermatogenesis Sequence
Spermatogonia (2n) -> Primary spermatocytes (2n) -> Secondary spermatocytes (n) -> 4 Spermatids (n)
-> 4 Spermatozoa (n)
118
Components of a sperm cell
1. Head
2. Midpiece
3. Flagellum
119
Head
*Contains genetic material
120
Midpiece
* Generates ATP from fructose
| * Filled with mitochondria, which generates the energy to be used as the sperm swims through female reproductive tract
121
Acrosome
* A cap that covers the head of sperm.
* Derived from Golgi Apparatus
* Required to penetrate the ovum
122
Flagellum
Required for motility
123
What organelle is in the midpiece?
Mitochondria
124
What organelle is the acrosome derived from?
Golgi Apparatus
125
Are the female reproductive organs external or internal?
Internal
126
What are the main gonads in females?
Ovaries
127
What hormones are secreted by the ovaries?
Estrogen and progesterone
128
What structure does the ovaries contain?
It contains thousands of follicles.
129
Follicle
Multilayered sacs that contain, nourish, and protect immature ova/eggs
130
How many eggs are ovulated into the peritoneal sac per month between puberty and menopause?
1 egg
131
Peritoneal Sac
Lines the abdominal cavity
132
Fallopian Tube/Oviduct
* Peritoneal sac leads into it
* It is lined with cilia, which propels the egg forward
* Site where fertilization occurs
133
Uterus
* Site where fetal development occurs
| * Fallopian tube connects to this muscular structure
134
Cervix
Lower end of the uterus
135
Vaginal Canal
* Connects to the cervix
* Site where sperm is deposited during intercourse
* Passageway through which childbirth occurs
136
Vulva
External female anatomy
137
Pathway for Female Reproductive System
Follicles in Ovaries -> Peritoneal Sac -> Fallopian Tube/Oviduct -> Uterus -> Cervix -> Vaginal Canal -> Vulva
138
Oogenesis
*Production of female gametes
139
In males, is the spermatogonia stem cells limited or unlimited?
There is an unending supply of spermatogonia stem cells.
140
In females, is the oogonia stem cells limited or unlimited?
* There is a limited supply of oogonia.
| * All the oogonia a woman will have are formed during fetal development.
141
Oogonia
Female reproductive stem cells
2n chromosomes
142
Primary oocytes
* The female reproductive cells at birth that have undergone DNA replication already.
* Birth -> Menarche
* Cells arrested in Prophase I
2n chromosomes
143
Secondary oocytes
*Cell that results from one primary oocyte completing Meiosis I per month
144
Menarche
* First menstrual cycle
| * One primary oocyte completes Meiosis I and produces a secondary oocyte and a polar body
145
How often does the menstrual cycle take place?
Once per month
146
Why is the polar body produced and not 2 complete oocytes?
It is a result of unequal cytokinesis.
| *Secondary oocyte has ample cytoplasm but polar body has very little to none.
