Chromosomes/Mitosis/Meiosis Flashcards
(86 cards)
1
Q
How are DNA molecules shaped?
A
Like a twist ladder called a double-helix
2
Q
What is the DNA molecule made of?
A
A sequence of four smaller nucleotides
3
Q
What are histones and what are their function?
A
Proteins, they compact DNA
4
Q
Why is DNA folded and compacted by the cell?
A
To allow it to fit in the nucleus and to make it easier to organize during cell division
5
Q
What is a chromosome?
A
It is a piece of double-stranded DNA with its own unique nucleotide sequence
6
Q
What is a chromatin?
A
All of the DNA in a cell’s nucleus, together with associated proteins.
7
Q
Where can chromosomes be found in extended form?
A
During the interphase
8
Q
Where can chromosomes be found in condensed form?
A
In M-phase (cell-division)
9
Q
What is a gene?
A
A sequence of DNA nucleotides that codes for a polypeptide
10
Q
What is a gene locus?
A
The specific physical location where a gene can be found on a chromosome
11
Q
What is the centromere?
A
A region of very concentrated chromatin on a chromosome that connects the P-Arm (shorter) and the Q-Arm (longer) of a chromosome
12
Q
What is a telomere?
And what is its function?
A
Repeated nucleotides at the end of the chromosome.
Prevent:
-DNA from getting shorter
-The ends of different chromosome
from attaching together
13
Q
What is after the s-phase?
A
The G2 phase
14
Q
What are sister chromatids?
A
They are two identical copies of a single chromosome that are joined together at a region called the centromere
15
Q
How many different types of chromosomes does an human cell have?
A
23 different types
16
Q
What differs from one type of chromosome to another?
A
They have a different set of genes.
17
Q
How many chromosomes are in each type of chromosome?
A
2, one from your mother (maternal) and one from your father (paternal)
18
Q
What is an homologous pairs?
A
A pair of chromosomes that contains similar genes arranged in the same order.
19
Q
What are diploid cells?
A
Cells that have 2 chromosomes of each type
20
Q
How do we count the number of chromosomes in a diploid organism?
A
nb. of chromosomes in a diploid organism = 2n, where n = the number of different types of chromosomes.
21
Q
What is a haploid cell?
A
A cell that has only one chromosome of each type
22
Q
Sex chromosomes are the type of chromosome that contains which genes?
A
The genes determining the sex of the organism
23
Q
What are autosomes chromosomes?
A
Any chromosome that is not a sex chromosome
24
Q
What is an homologous pair?
A
A pair of chromosomes (one from each parent)
- Carry the same types of genes in the same locations (loci),
But they may have different versions of those genes (called alleles)
25
Autosomes come in __________ pairs?
homologous
26
How can a homologous pair be homologous?
They need to have the similar genes arranges in the same order
27
Is the sex chromosome homologous? If not, why?
They are not considered homologous since the X and the Y chromosomes have different genes
28
What causes down syndrome?
Where there's 3 copies of chromosome #21
29
What's the cause of Klinefelter syndrome?
When the offspring inherits **XXY**
30
What's the cause of Turner syndrome?
When the offspring inherits one X chromosome
31
The asexual reproduction process in eukaryotic cell is called
mitosis
32
What is asexual reproduction? And how are they genetically?
It's when a cell divides into two new daughter cells. They are both genetically identical to each other and to the original cell
33
How does asexual reproduction proceeds for prokaryotes, and eukaryotes?
Binary fission (prokaryotes), Mitosis (eukaryotes)
34
What is a gamete?
It is a sex cell used in sexual reproduction. It contains half the number of chromosomes (haploid) compared to a regular body cell (diploid)
35
What are the two main types of gametes?
Sperm (male gamete)
Egg (female gamete)
36
What is sexual reproduction?
It is when an egg and sperm are required to unite to create a new genetically distinct organism.
37
The egg and sperm are called..
gametes
38
Is sexual reproduction made by prokaryotes?
No, only eukaryotes
39
What does eukaryotes use to make sexual reproduction?
Meiosis
40
Which processes do eukaryotes use for sexual reproduction?
Eukaryotes use **meiosis** to make **gametes**, and then **fertilization** (**gamete fusion**) to create a new organism.
41
What are somatic cells?
They are cells that in a multicellular eukaryote, that divide asexually and don't form gametes
42
What are primary sex cells?
Cells that divide by meiosis to form gametes
43
What happens in mitosis? What are the products like, genetically?
One cell divides into two new daughter cells each genetically identical to each other and to the original cell
44
When does mitosis occurs for almost all the cells in the body?
M-phase
45
Which cell type is mitosis used by?
used by **all single-celled eukaryotes** and **most cells of multi-cellular eukaryotes** (plants, animals, fungi)
46
What are two important divisions in mitosis
A nuclear division and one cytoplasmic division
47
The four phases of cell mitosis are..
1) Prophase
2)Metaphase
3)Anaphase
4)Telophase
48
What does the telophase phase of mitosis includes?
Cytokinesis (the division of the cytoplasm)
49
What are the 5 cellular events happening in the phase one of mitosis? (prophase)
1) Chromosomes compacts
They become more compact as the chromatin they are made of condenses
2) Spindle microtubules begin to form from centrioles
3) The nucleolus disappears
4) Nuclear envelope dissolve
5) Spindle microtubules attach to the kinetochore of each chromatid and the centrioles move to each pole of the cell
50
What is the cellular event happening in the phase two of mitosis? (metaphase)
1) All chromosomes are aligned midway between the two spindle poles
The two kinetochores pull on the spindle microtubules until the duplicated chromosomes are lined up at the equator of the cell
51
What are the two cellular events happening in phase three of mitosis? (anaphase)
1) The centromeres are duplicated
2) The spindle microtubules pull each sister chromatid apart to each opposite pole of the cell
Sister chromatids separate and move toward opposite spindle poles. At the moment of separation, each sister chromatid becomes an individual chromosome
52
What are the five cellular events in the fourth phase of mitosis? (telophase and cytokinesis)
In telophase:
1) Spindle microtubules disappear.
2) Nuclear membranes reform around
the two sets of genetic materials.
3) The chromosomes relax back into extended chromatin
4) Nucleolus reappears
5) Cytokinesis occurs and the dividing cell splits into two
(undoing what happened in prophase)
53
How does cytokinesis occurs in plant cells?
Many small vesicles **deposit carbohydrates** along the **midplane**.
The carbohydrates solidify to form a **cell plate**, which will become the new cell wall.
(just build a wall in-between)
54
How does cytokinesis occurs in animal cells?
**Microfilaments of the cytoskeleton** form a ring around the **plasma membrane** which tightens to form a **cleavage furrow**
The cleavage furrow gets deeper and deeper until the cytoplasm is cut in two
(ex: pulling on a string around a balloon)
55
What is called the process of gamete formation in eukaryotes?
Meiosis
56
What is an allele?
A different version of the same gene
57
In an homologous pair of chromosomes, can the two homologous chromosomes have different alleles of a gene?
Yes, they can have the same alleles of a gene of different alleles
58
What is the main reason why so many organism use sexual reproduction?
It leads to genetic variation
59
How does sexual reproduction proceed to give its product (cells) the genes that they have? And what does it provide to the population?
Sexual reproduction **selects randomly** the **alleles** of the two parents, giving the offspring a **unique combinaison** of the two patents' gene.
Resilience against extinction.
60
What does meiosis results?
Formation of gametes (oocytes (female gametes) and spermatocyte (male gametes ))
61
How many chromosomes does a gamete have?
Half the number of a normal diploid cell. (haploid)
62
During sexual reproduction, what needs to fuse in order to create an offspring? When does this happens?
Two **gametes**
After meiosis (**gamete fusion**/fertilization)
63
Meiosis happens to which cells? What are they?
Primary sex cells
The cells that will divide using meiosis to provide female and male gametes
64
Does meiotic division reduce the number of chromosomes in each cells?
Yes
The total number of chromosomes is reduced by meiosis to produce gametes. And gametes are haploid.
65
How many division rounds does meiosis involves? And what are they called?
It involved two rounds of nuclear and cytoplasmic division
In meiosis I, and in meiosis II
66
What are the stages of meiosis I?
1) Prophase I
2) Metaphase I
3) Anaphase I
4) Telophase I and cytokinesis
67
In prophase I, which events are different than mitosis prophase? What are they?
1) Tetrad formation: duplicated chromosomes of each type will attach to each other to form tetrads, instead of being organized separately.
2) Homologous recombination: while in tetrads, one chromatid from an homologous can overlap with another chromatid and exchange alleles.
| ok
68
What does homologous recombination increase?
Genetic variability
69
What's the meaning of the word chiasma?
The **physical location** where the two chromatids overlap and **homologous recombination** takes place.
70
What is the event that is different in Metaphase I of Meiosis I than mitosis metaphase? And what is it doing?
1) Independent assortment:
homologous chromosomes line up together as **tetrads**, instead of individually. The duplicated homologous chromosome that forces the "north" or "south" pole of the cell is completely **random** for every type of chromosome (including sex chromosomes)
| way that the homologous pairs line up is completely random
71
What does independent assortment does to genetic variability?
It increases it.
72
What are the phases of meiosis I, Anaphase I, different than those in mitosis?
1) The centromeres are are not duplicated
2) The duplicated homologues are pulled apart from each other, instead of individual chromatids pulled apart.
73
What are the events different in meiosis I, telophase I from mitosis telophase
1) The chromosomes do not relax back into extended chromatin
2) The nuclear membrane does not re-form
3) The nucleolus does not reappear
74
75
What's the result of meiosis II?
**Four haploid gametes**, each having one set of genetic material
75
What are the steps that are the same in meiosis II prophase II and mitosis prophase?
- Spindle microtubules start to form from the centrioles
- The spindle microtubules attach to the kinetochore of each chromatid and the centrioles move to each pole of the cell.
76
What are the differences between prophase II and mitosis prophase?
- chromatin is already in condensed form from prophase I
- nucleolus is already gone
- nuclear membrane is already gone
77
What is the product of telophase II?
4 haploid cells
77
Is anaphase II proceeding the same way as anaphase in mitosis? If so, how do it occurs?
Yes
1) The **centromeres** are **duplicated**
2) The **spindle microtubules** pull on each **sister chromatids** apart to each **opposite pole** of the cell
77
Is metaphase II the same as mitosis metaphase? If so, what is its cellular processes?
Yes
The **two kinetochores** pull on the **spindle microtubule** until the duplicated chromosomes are **lined up** at the cell's equator
78
Is telophase II proceeding the same way as telophase in mitosis? If so, how does it occur?
Yes
1) The spindle microtubules disappear
2) The nuclear membrane reform around the two sets of genetic materials
3) The chromosomes relax back into extended chromatin
4) The nucleolus reappear
5) Cytokinesis happen, and the dividing cell is splits into two.
79
Gamete fusion is part of ______ ____________ but not part of _______.
Gamete fusion is part of sexual reproduction but not part of meiosis
80
What is gamete fusion (fertilization)?
It's a third way that sexual reproduction increases gene variability
| process where a male and a female gamete join together form a zygote
81
When does gamete fusion occurs?
After meiosis
82
Why does gamete fusion (fertilization) increase the gene variability?
It **mixes up** the **chromosomes** (and therefore the combinations of alleles) of two genetically distinct organism.
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