Reproduction Flashcards
1
Q
Are autosomal cells haploid or diploid?
A
Diploid (2n, contain two copies of each chromosome)
2
Q
Are germ cells haploid or diploid?
A
Haploid (n, contain one copy of each chromosome)
3
Q
What is Interphase?
A
- includes the first 3 stages of cell cycle (G1, S, G2)
- longest part of cell cycle
- 2 centrioles come together to form a centrosome – helps hold chromosomes apart
- chromosomes are uncondensed
- individual chromosomes are not visible with light microscopy b/c they are in chromatin form (less condensed form where DNA is available to RNA Poly for transcription)
4
Q
What is the G0 stage?
A
stage where cells that do not divide spend all of their time, cell just performs its function
5
Q
What happens during the G1 stage?
A
- Presynthetic gap
- cells create mitochondria, ribosomes, ER
- cells increase in size
- DNA is examined and repaired at restriction point (determines if cell can enter next stage)
6
Q
What happens during the S stage?
A
- Synthesis of DNA
- cell replicates its DNA
- after replication each chromosome has 2 identical chromatids bound together at the centromere
- have 92 chromatids organized into 46 chromosomes organized into 23 homologous pairs
- 2x as much DNA as cells in G1
7
Q
What happens during G2 stage?
A
- Postsynthetic gap
- cell continues to grow & replicates organelles in preparation for mitosis
- cell continues to perform its normal functions
- goes through 2nd quality control checkpoint
8
Q
What happens during M stage?
A
- Mitosis (cell division)
- cytokinesis (splitting of the cytoplasm and organelles into two daughter cells)
9
Q
What composes a chromatid?
A
a complete double-stranded molecule of DNA
10
Q
What is a sister chromatid?
A
identical copies of eachother
11
Q
When can the term chromosome be used in the cell cylce?
A
- before S phase when referring to a single chromatid
- after S phase when there is a pair of chromatids attached at the centromere
12
Q
What is the result of division in autosomal cells?
A
2 genetically identical daughter cells
13
Q
What is the result of division in germ cells
A
2 non-equivalent germ cells
14
Q
When are the checkpoints in the cell cycle?
A
- between G1 and S phase
- between G2 and M phase
15
Q
What occurs at the G1/S checkpoint?
A
- known as the restriction point
- cell determines if DNA is good enough for synthesis
- if there is damaged DNA then cell goes into arrest until DNA is repaired
16
Q
What is the main protein in control during the G1/S checkpoint?
A
p53
17
Q
What occurs at the G2/M checkpoint?
A
- ensure the cell has achieved adequate size and organelles have been properly replicated
- makes proteins for mitosis
18
Q
What protein plays a role during the G2/M checkpoint?
A
p53
19
Q
What molecules are responsible for the cell cycle?
A
cyclins & cyclin-dependent kinases (CDK)
20
Q
Explain the process of cyclin & CDK binding and what they do
A
cyclins bind to CDKs to create an active CDK-cyclin complex (MPF - mitosis promoting factor) that can then phosphorylate transcription factors that promote transcription of genes required for the next stage of the cell cycle
21
Q
How does cancer occur?
A
results when cell cycle control is deranged and damaged cells still undergo mitosis
22
Q
What gene is most commonly mutated in cancer?
A
TP53 (gene that produces p53)
23
Q
What is metastasis?
A
spread of cancerous cells through the blood stream or lymphatic system
24
Q
What is mitosis?
A
- process by which two identical daughter cells are created from a single cell
- occurs in somatic cells
25
What are the phases of mitosis?
PMAT
1. prophase
2. metaphase
3. anaphase
4. telophase
26
What is a centrosome?
contains two tubulin-based centrioles responsible for proper movement of chromosomes
27
(1) What occurs during prophase?
| (2) What occurs during Prometaphase?
(1)
- condensation of chromatin into chromosomes -- chromosomes condense
- centriole pairs (located outside the nucleus in the centrosome) separate and move towards opposite poles of cell
- at opposite poles of cell the centrioles begin to form spindle fibers / mitotic spindle (made of microtubules)
- some microtubules form asters (anchor centrioles to cell membrane) and others extend toward middle of cell
(2)
- nuclear membrane dissolves so spindle fibers can contact the chromosomes
- kinetochores appear at centromere and serve as attachment points for fibers of the spindle apparatus that are called kinetochore fibers
28
What occurs during metaphase?
- centriole pairs located at opposite ends of cell
- chromosomes gather along metaphase plate in center of the cell under guidance of spindle apparatus
- chromosomes are madeup of two sister chromatids that are still attached to one another (pair of sister chromatids = one chromosome_
29
What occurs during anaphase?
- centromeres split so each chromatid has its own distinct centromere and sister chromatids can separate
- sister chromatids pulled toward the opposite poles of the cell by shortening of kinetochore fibers
30
What occurs during telophase?
- spindle apparatus disappears
- nuclear membrane reforms around each set of chromosomes
- nucleoli reappear
- chromosomes decondense back into chromatin
- cell divides into two identical daughter cells
31
What is meiosis?
- occurs in gametocytes (germ cells)
| - results in up to 4 non-identical sex cells (gametes)
32
What are similarities between mitosis and meiosis?
- genetic material is duplicated
- chromatin is condensed into chromosomes
- microtubules from centrioles are involved in dividing genetic material
33
What are differences between meiosis and mitosis?
-consists of one round of replication followed by two rounds of division
34
How many homologous pairs of chromosomes (homologues) does the human genome have?
23 (with one chromosome inherited from each parent)
35
What are sister chromatids?
identical strands of DNA connected at the centromere
36
What are the phases of meiosis?
```
Meiosis 1
-prophase 1
-metaphase 1
-anaphase 1
-telophase 1
Meiosis 2
-prophase 2
-metaphase 2
-anaphase 2
-telophase 2
```
37
What occurs during prophase 1?
- chromatin condenses into chromosomes
- spindle apparatus forms
- synapsis: process by which homologous chromosomes come together and intertwine, each chromosome now consists of 2 sister chromatids so each synaptic pair contains 4 chromatids and is called a tetrad
- crossing over: occurs when chromatids of homologous chromosomes break at the poi t of contact (chiasma) and exchange equivalent pieces of DNA, increases genetic diversity
38
What is a synaptonemal complex?
group of proteins that hold homologous chromosomes together; part of tetrad
39
What is linkage?
- associated with crossing over
- tendency of genes to be inherited together
- genes located farther from eachother are less likely to be inherited together and more likely to undergo crossing over relative to eachother
40
How does crossing over explain Mendel's 2nd Law?
- law of independent assortment
| - states that inheritance of one allele has no effect on the likelihood of inheriting certain alleles for other genes
41
What occurs during metaphase 1?
- homologous pairs (tetrads) align at metaphase plate and each pair attaches to a separate spindle fiber by its kinetochore
- at this phase in mitosis each chromosome is lined up at the plate but is attached to two spindle fibers -- one fro each pole
42
What occurs during anaphase 1?
- homologous pairs separate and are pulled to opposite poles of cell
- disjunction: each chromosome of paternal origin separates from its homologue of maternal origin and either chromosome can end up in either daughter cell thus distribution of homologous chromosomes to 2 intermediate daughter cells is random with respect to paternal origin
43
What is segregation?
- occurs during anaphase 1
| - separating of 2 homologous chromosomes
44
What law does anaphase 1 follow?
Mendels 2nd Law of independent assortment
45
What occurs during telophase 1?
- nuclear membrane forms around each new nucleus (each chromosome consists of 2 sister chromatids joined at centromere)
- cells now haploid (23 chromosomes)
- cell divides into 2 daughter cells by cytokinesis
46
What is interkinesis?
- occurs during telophase 1 between cell divisions
| - short rest period that sometimes occurs between cell divisions and chromosomes may partially uncoil
47
What is the result of meiosis 1?
- homologous chromosomes are separated
- chromosome number is halved (reductional division)
- daughter cells have haploid number of chromosomes (23)
48
What occurs during prophase 2?
- nuclear envelope dissolves
- nucleoli disappears
- centrioles migrate to opposite poles of cell
- spindle apparatus begins to form
49
What occurs during metaphase 2?
- chromosomes line up on the metaphase plate
| - 1 chromosome per daughter cell
50
What occurs during anaphase 2?
- centromeres divide
- chromosomes separate into sister chromatids that are pulled to opposite poles by spindle fibers
- 2 chromosomes in each daughter cell
51
What occurs during telophase 2?
- nuclear membrane forms around each new nucleus
- cytokinesis follows and 2 daughter cells are formed
- final product is 4 haploid daughter cells per gametocyte
- one chromosome in each daughter cell
52
What is the result of meiosis 2?
- separation of sister chromatids (equational division)
- more similar to mitosis than meiosis 1
- 4 haploid daughter cells with one chromosome in each
53
Mitosis Key Points
- 2n -> 2n
- occurs in all dividing cells
- homologous chromosomes do not pair
- no crossing over
54
Meiosis Key Points
- 2n -> n
- occurs in sex cells only
- homologous chromosomes align on opposite sides of metaphase plate
- crossing over can occur
55
What is biological sex determined by?
the 23rd pair of chromosomes
56
What are kinetochores?
- proteins and RNA around the centromere
| - facilitates the binding of microtubules to the spindle
57
At the end of mitosis, ____ gets degraded while ___ stays around in its inactive form
- cyclin (concentration fluctuates)
| - CDK (concentration remains constant)
58
___ activity represents the start of mitosis
MPF
(cyclin and CDK bound together
)
59
Proto-Oncogenes
- genes that aid in cell growth
- gene that is active during checkpoint
- this is the form that is not mutated
60
Oncogene
- mutated form of the proto-oncogene
- permanently turned on form of the proto-oncogene so surpasses all checkpoints
- cell is unable to stop growing
- "gain of function" mutation
61
Tumor Supressor Genes
- typically inhibit growth
- when mutated it becomes non-functional and can no longer inhibit growth
- "loss of function" mutation
62
Apoptosis
- coordinated collapse of the cell
- protein degradation and ladder-like DNA fragmentation occur
- neighboring cells engulf the leftover cell bits
- important in embryonic cell death
- cell shrinks (condensation)
- membranes stay intact
- ATP required
- only affects individual cells
63
What makes a cell decide to undergo apoptosis?
- withdraw positive growth signals (ex. take away growth factor for neurons)
- receipt of negative signals (includes increased levels of oxidative damage, DNA damage, death activators like FasL)
64
Necrosis
- cellular swelling
- ATP depletion
- cell lysis (burst) which leads to an inflammatory reaction
- membranes are broken
- DNA is fragmented randomly and smeared
- in vivo, whole areas of tissue are affected
