BIOL2030 > Module 1 > Flashcards

Module 1 Flashcards

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1
Q

What is DNA?

A

DNA - deoxyribonucleic acid - is the hereditary material in humans and almost all living organisms.

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2
Q

What are nucleotides?

A

Nucleotides are the monomers making up the DNA polymer sequence.

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3
Q

What is a gene?

A

Genes are units of hereditary information; DNA is an information storage system.
- Genes are made up of many nucleotides and said genes will encode for a protein.

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4
Q

What does DNA and genes determine?

A

DNA and genes determines an organisms phenotype.
- Note: phenotypes are not passed on, rather genotypes are inherited.

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5
Q

What information is inherited in DNA?

A

DNA information is copied and inherited, but the phenotype is NOT.

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6
Q

Where in the DNA is information encoded?

A

Information is encoded in the molecular structure of genes on chromosomes

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7
Q

What is chromatin?

A

Chromatin is a complex of DNA and protein found in eukaryotic cells.

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8
Q

What are the different sizes of DNA from helix to chromosome?

A

helix - 2nm
nucleosome - 11nm
chromatin fibers - 30nm
chromatin - 300nm
chromosome - 700nm

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9
Q

Process of condensing DNA?

A

The helix is organized into nucleosomes by histone molecules, histones are condensed into chromatin fibers. During mitosis, they condense even more into chromosomes.

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10
Q

At what stage of condensation are genes inaccessible? c

A

Genes are not accessible to be transcribed when nucleosomes end up being condensed/organized into chromatin fibers.

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11
Q

What is a eukaryotic chromosome?

A

A eukaryotic chromosome is a linear molecule of DNA associated with histone proteins and packaged into higher order structures.

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12
Q

What is a telomere?

A

Telomeres are the stabile ends of linear chromosomes

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13
Q

What are centromeres?

A

A centromere is the constricted region of a chromosome where the kinetochore forms and spindle microtubules attach during cell division.
- Sister chromatids are held together at the centromere (referred to as the primary constriction)

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14
Q

What is a locus?

A

A locus is the position of a gene on a chromosome, or. particular location on a chromosome. (plural is loci)

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15
Q

In what ways can chromosomes physically differ?

A

Eukaryotic chromosomes differ in size and morphology
- might depend on centromere location for example

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16
Q

What are the 4 different locations of centromeres?

A

metacentric: middle
submetacentric: slightly off-centre
acrocentric: mostly off-centre
telocentric: located at/next to telomere

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17
Q

What is meant by haploid?

A

Haploid (N) contains one copy of genetic materials subdivided into chromosomes.
- nonhomologous chromosomes (only one of them is present so it cannot be homologous)

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18
Q

Haploid examples?

A

Some eukaryotes (like certain yeasts) have a haploid genome.

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19
Q

What is meant by diploid?

A

Diploid (2N) contains two copies of genetic material subdivided into chromosomes.
- they would be like homologous chromosomes (2 identical chromosomes with the same genes, but different alleles typically)

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20
Q

Diploid examples?

A

Many eukaryotes (like ourselves) have a diploid genome. We have 23 homologous pairs of chromosomes, or 46 chromosomes in total.

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21
Q

Allelic variations on homologous chromosomes?

A

Two copies of homologous genes may show allelic variation at a locus. These genes code for the SAME TRAIT, but might have variations.
- Different alleles changes the protein made and the phenotype we will see.

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22
Q

What are autosomes?

A

Autosomes are chromosomes that are the same in males and females

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23
Q

What are sex chromosomes?

A

Sex chromosomes are a pair of chromosomes that differs between females and males.

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24
Q

Matched, unmatched and only one sex chromosomes example?

A

Matched: XX = female
Unmatched: XY = male
Only one: XO

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25
What DNA is in our genome in total? Where does it all come from?
We have 22 pairs of autosomes and 1 pair of sex chromosomes, as well as mitochondrial DNA. - 1 haploid set (23 chromosomes) comes from each parent and mitochondrial DNA comes from the maternal parent.
26
How many chromosomes and nucleotides do we have?
We have 46 chromosomes and 2.3 billion nucleotides.
27
What is an example of genes being on the same chromosomes?
Blood type is encoded by a gene on chromosomes 9, where the allele can be A, B or O. The combination of the alleles you possess determines your blood type. - a single base change is likely located at the active site involved in sugars and antigen formation, informing us of our blood type.
28
What are important facts about human genetics? How do we pass information along, what do genes encode?
Humans are diploid - pass only one copy of a gene to the next generation - genes encode information - we pass information to the next generation - we do not pass on the material phenotype
29
Bacterial DNA shape?
Prokaryotic cells contain a single circular chromosome made up of double-stranded DNA
30
Bacterial DNA replication?
The chromosome replicates and the origins segregate to opposite sides - The cell divides and each new cell has an identical copy of the original chromosome.
31
How does eukaryotic cell reproduction differ from prokaryotic cell reproduction?
This is when we are dealing with multiple linear chromosomes rathe than one circular chromosome.
32
Features shared and unique between prokaryotic and eukaryotic cell reproduction?
Shared: copy each chromosome, and separate DNA into each daughter cell Unique to eukaryotes: accommodate nuclear envelope, ensure that exactly one copy of each linear DNA strand ends up in each daughter cell
33
What are the different stages of the cell cycle? Include checkpoints?
G0 - resting phase G1 - growth of cell, preparation of nutrients G1/S CHECKPOINT S - cell duplication G2 - production of cellular machinery for mitosis G2/M CHECKPOINT M (mitotic) phase - cell division SPINDLE-ASSEMBLY CHECKPOINT Cytokinesis - cell division (physical)
34
What is the kinetochore?
The kinetochore is a complex of proteins that assembles at the centromere and serves as the site of microtubule attachment during the process of cell division
35
What are spindle microtubules?
Spindle microtubules are filaments responsible for moving chromosomes during cell division.
36
What are sister chromatids?
Sister chromatids are composed of two linear chromatids that are connected by a centromere. The chromatids will be genetically identical (except in meiosis where crossing over can occur)
37
What is 1 centromere equal to?
1 centromere = 1 chromosome by definition - sister chromatids attached by the centromere are considered one chromosome, but 1 linear chromosome with 1 centromere is also considered one chromosome.
38
Why does linear DNA remain close after the S phase?
Linear DNA has been replicated in the S phase, but remain in close association with each other because they are physically connected at the centromere (until anaphase).
39
How many strands of DNA exist in the following stages: prior to S and after S?
Prior to S = 1 linear strand After S = 2 linear strands - Note: they would not be maximally condensed at this time, they would condense during mitosis!
40
What are the phases of mitosis?
1. Interphase 2. Prophase 3. Prometaphase 4. Metaphase 5. Anaphase 6. Telophase
41
What happens during interphase?
The cells go through G1, S and G2 phases and are growing and forming the technology they will need to undergo mitosis. DNA also duplicates at this time. - DNA is not condensed at this time, nuclear envelope is intact.
42
What happens during prophase?
The nuclear envelope is still intact, centrosomes move to either pole of the cell, and DNA condenses into chromosomes. - SPindles also develop.
43
What happens during prometaphase?
The nuclear envelope disintegrates, and the mitotic spindles attach to the centromeres of the chromosomes.
44
What happens during metaphase?
The chromosomes line up along the metaphase plate, attached to their centromeres are the spindle fibers.
45
What happens during anaphase?
During anaphase, the chromosomes separate as the spindles pull the sister chromatids apart. Equal number of daughter chromosomes are pulled to each side, dividing genetic material equally. - Known as the physical separation of sister chromatids, which become chromosomes.
46
What happens during telophase?
The cells physically divide as the cleavage furrow separates into two daughter cells, each containing the same amount of information. - nuclear envelopes reform!
47
When do chromosomes become maximally condensed?
Chromosomes only become maximally condensed during mitosis.
48
What are common features of mitosis: cytoplasm amounts, genome content, daughter cell genome?
- The cytoplasm is often reduced by about 1/2 - There is no net change in genome content over time - Each daughter cell gets exactly 2 haploid sets of chromosomes (making them diploid)
49
What is the main point of meiosis?
The point of meiosis is to make gametes for reproduction
50
What is meiosis?
Meiosis is the production of haploid (n) gametes. - "n" refers to one set of chromosomes
51
What is fertilization?
Fertilization is the restoration of the diploid state (2n) in the next generation.
52
How are diploid organisms produced?
Diploid organisms are produced by the fusion of 2 haploid gametes. - During meiosis, haploid gametes are produced, then the fertilization of the gametes causes them to form a diploid organism that grows into another organism that will reproduce through their gametes.
53
What does sexual reproduction maintain?
Sexual reproduction maintains the correct diploid state across generations.
54
What is the meiotic cell cycle? Going from G1 to cells produced?
1. G1 (1 diploid cell - 2N) 2. S (DNA replication - 2N) 3. G2 4. Meiosis I (reductive cell division -N) 5. interkinesis 6. Meiosis II (equational division N-N) 7. 4 haploid (N) cells - Meiosis II needed to make sure that 1 chromosome equals 1 linear DNA molecule.
55
Stages of Meiosis?
1. Prophase I 2. Metaphase I 3. Anaphase I 4. Interkinesis 5. Metaphase II 6. Anaphase II 7. 4 daughter cells (n)
56
What occurs during prophase I?
There are 5 substages of prophase I - pairing of homologous chromosomes - synapsis - tetrad (bivalent) structures - crossing over - visible chiasmata
57
What physically happens during prophase I of meiosis?
Homologous chromosomes pair up
58
What happens during metaphase I?
23 homologous pairs line up along the metaphase plate
59
What occurs during anaphase I?
Centromeres do NOT split as the homologous pairs are pulled apart. - This will cause the chromosome count to go down by half after cytokinesis.
60
What happens during metaphase II?
Sister chromatids line up along the metaphase plate
61
What happens during anaphase II?
Centromeres split as chromosomes are puled apart. - This restores the 1:1 relationship between linear DNA molecules and chromosomes
62
How are meiosis I and meiosis II different? Which stage of meiosis looks like mitosis?
While meiosis I is a reductive process, going from diploid to haploid (2N-N) meiosis II is equational, going from N-N. - Meiosis II is more similar to mitosis in practice.
63
What are the two forms of genetic variation that arises from the process of cell reproduction?
1. New combinations of alleles for genes on the same chromosome 2. Different combinations of chromosomes within the haploid sets found in gametes
64
Amount of genetic material at the beginning vs end of meiosis?
Beginning: 2N (diploid) End: N (haploid)
65
What happens during middle prophase I?
During middle prophase I, DNA condenses into chromosomes (now visible)
66
What happens during late prophase I?
During late prophase I, homologous chromosomes pair up.
67
What else happens during late prophase I?
Chiasmata events or crossing over happens during this phase.
68
What happens during metaphase I?
The homologous pairs chromosomes line up along the metaphase plate
69
What happens during anaphase I?
The homologous pairs separate (NO CENTROMERES BROKEN)
70
What happens during telophase I?
WE have 2 new cells with haploid material.
71
Despite having the clear phases of meiosis, does everything happen sequentially?
No, meiosis is a continuous process and it happens really fast. There are still phases of meiosis, but they blend between one another, translating from one phase to another seamlessly as fast as possible.
72
What is crossing over?
Crossing over is the physical exchange of genetic material among non-sister chromatids (chromatids that are not physically connected by a centromere)
73
What is the first source of genetic variation?
Crossing over is the first source of the genetic variation in meiosis.
74
How does crossing over occur?
Crossing over is when two alleles (same gene) on chromosomes phsycially interact and cross over (meaning that a large A is swapped for a small a). - This means that there are new combinations of alleles on the same linear DNA molecule. This genetic variant would not have existed on the parental type (starting material) - We then undergo meiosis I and II
75
When does crossing over occur?
The process of crossing over - the exchange of genetic material among non-sister chromatids - occurs during prophase I.
76
What occurs in the gametes due to crossing over?
Due to crossing over, there are now NEW combinations of alleles on these chromosomes.
77
What is the second source of genetic variation?
The second source of genetic variation is the independent assortment of chromosomes into gametes when they line up on the metaphase plate.
78
What is meant by the independent assortment of chromosomes into gametes?
The pairs align independently of each other on the metaphase plate. - For example, there might be 3 homologous pairs of chromosomes, they could line up 4 different ways, producing a vast variety of genetic variation. - This is due to RANDOM ASSORTMENT
79
What is the yield of independent assortment of chromosomes into gametes?
Independent assortment of chromosomes into gametes yields different combinations of maternal and paternal chromosomes within haploid sets found in gametes.
80
What is N?
N is the number of homologous gene pairs.
81
What is the number of genetic combinations given by?
The number of possible genetic combinations is given by 2^N. - Base of 2 is due to the diploid set of genetic material.
82
Human combinatorial variation?
We have 23 homologous gene pairs. Combinations = 2^23, which is around 8 million possibilities.
83
When does crossing over occur?
Crossing over occurs during prophase I
84
When does independent assortment occur?
Independent assortmet of chromosomes occurs during metaphase and anaphase I
85
What is the first source of genetic variation?
Crossing over
86
What is the second source of genetic variation?
Independent assortment of chromosomes
87
What does meiosis yield?
Meiosis yields 4 haploid daughter cells called gametes. - Meiosis yields haploid cells genetically different from one another - Meiosis yields genetic chromosomes different from the parent.
88
How does meiosis maintain diploid DNA?
In conjunction with the fusion o f gametes, meiosis maintains levels of DNA in sexually reproducing organisms.
89
What are the two combinatorial genetic processes that permit the tremendous genetic diversity?
- Independent assortment of paternal and maternal chromosomes (source 2) - Crossing over between non-sister chromatids (source 1)
90
What would independent assortment of chromosomes shuffle?
Independent assortment of chromosomes shuffles the alleles of genes on different chromosomes. - Ex. One cross might have the defective/bad gene whilst the other cross might optimize the health of the organism resulting from this random assortment.
91
When will independent assortment not work?
Independent assortment of chromosomes will not work on same chromosome alleles.
92
Result of indepedent assortment?
Two equally probably arrangements of chromosomes at metaphase I will result in daughter cells with a lot of genetic variation following metaphase II.
93
Independent assortment effects on alleles of genes on the same chromosomes?
The two equally probably arrangements of chromosomes at metaphase I will still result in faulty/poor gametes to be produced following metaphase II
94
What does crossing over of non-sister chromatids shuffle?
Crossing over of non-sister chromatids does shuffle the alleles of genes on the same chromosome. - Through crossing over process, we can separate good and bad alleles to get the combinations we would like.
95
Advantage of crossing over vs independent assortment?
Crossing over CAN shuffle the alleles of genes on the same chromosome, which is effective in cases where the traits we are selecting for lie on the same chromosome.
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