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Biology🧪🌱💦 > Lecture 9 > Flashcards

Lecture 9 Flashcards

1
Q

Little recap from chapter 8:
How many Stages of Cell Cycle + name them

A

2 Stages of Cell Cycle:
1) Interphase
2) Mitotic phase

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2
Q

Name the 3 main things that happen in Interphase

A

G1 -normal growth
S -chromosomes copied (synthesis)
G2 -final growth/preparation for division

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3
Q

Little explanation of what happens in the mitotic phase:

A

4 steps: Prophase, Metaphase, Anaphase and Telophase (PMAT)
- distribution of chromosomes
- each daughter cell gets an EXACT COPY of the parent cell’s chromosomes

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4
Q

What is truly the last step but is not included in mitosis?

A

cytokinesis (separation of the 2 daughter cells)

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5
Q

What is an asexual reproduction?

A

organisms reproduce offspring that are EXACT copies of themselves
+ A single individual is the SOLE parent to donate all of its genes to its offspring

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6
Q

What is a sexual reproduction?

A

2 parents produce offspring (that have unique combinations of genes inherited from the 2 parents)

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7
Q

Through sexual reproduction, does it vary genetically or are they clones?

A

SEXUAL: vary genetically
Asexual: clones

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8
Q

How do humans reproduce?

A

by sexual reproduction

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9
Q

In humans, how many chromosomes does each somatic cell have?

A

46 chromosomes

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10
Q

What are somatic cells?

A

all cells other than sperm and ovum

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11
Q

How many chromosomes do our sex cells (sperm & eggs) have?

A

they have 23 chromosomes

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12
Q

What does mitosis ensure?

A

Ensures that each daughter cell gets an EXACT COPY of the genetic information from
parent cell (Daughter cells are clones of original parental cell)

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13
Q

TRUE OR FALSE:
In a sexual reproduction, the offspring are identical to the
parents.

A

FALSE, they are not identical

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14
Q

What cycle do we use to produce gametes?

A

we use MEIOSIS

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15
Q

How different are they?

A
  • differ genetically from the parents
  • and also from each other
    (all genetically different)
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16
Q

Meiosis (sex-cell formation) occurs in cells that will become what?

A

that will become gamete cells

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17
Q

What produces sperm in males?

A

spermatocytes

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18
Q

Spermatocytes produce sperm via what?

A

meiosis
(product (sperm) are all genetically different)

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19
Q

how are spermatocytes produced?

A

Through mitosis

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20
Q

What will produce eggs in females?

A

primary oocytes

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21
Q

the eggs are produced from primary oocytes via what?

A

meiosis

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22
Q

How are the primary oocytes produced?

A

by mitosis

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23
Q

Meiosis produces cells that:
(2 important factors)

A

1) have ½ the # of chromosomes found in the original parent cell
2) are genetically different from parent cells (& each other)

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24
Q

Why halve chromosomes #?

A

human cells contain 46 chromosomes
if chromosome # is not halved, then egg with 46 + sperm with 46
will make a child with 92
then 92 + 92 = 184 ….
(so # of chromosomes would double)
therefore, meiosis keeps chromosome# CONSTANT (b/w each new generation (offspring))

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25
How are there 23 pairs? how much from each parent?
1 complete set of 23 chromosomes from mom 1 complete set of 23 chromosomes from dad 23 + 23 = 46 TOTAL
26
In a human somatic cell, there are 46 chromosomes 1) how many pairs?
23 homologous Pairs
27
Difference b/w diploid and haploid cells?
Diploid: cells with 2 sets of chromosomes Haploid: cells with 1 set of chromosomes So Diploid = 2Haploid N = 2N
28
Are homologous pairs of chromosomes identical?
No, not identical, just similar
29
Finish the sentence: Homologous chromosomes code for the _____ _____
for the same genes So basically homologous regions code for the same gene
30
These same genes, do they have different or identical alleles?
DIFFERENT ALLELES (different versions of that gene (brown vs blue))
31
What are alleles?
an alternative version of a gene
32
Give an example of an allele
the gene for flower color in pea plants exist in 2 versions: – 1 for purple flowers and the other for white flowers
33
Do alleles control the same character or different?
The same character BUT do not necessarily contain the same info (purple vs blue)
34
What are the 2 major genes for eye color?
one that controls for brown or blue one that controls for green or hazel other genes modify the above genes
35
LET'S DO A QUICK RECAP ON ALL OF THIS
(to understand the main components of what meiosis is (w/o the steps))
36
1. # of chromosomes in a somatic cell 2. how many pairs of chromosomes? 3. Arranged in sets of how many?
1. 46 2. 23 pairs 3. sets of 2 (1 mom + 1 dad)
37
What does the offspring get?
only one set from each parent
38
Goal of meiosis
convert diploid parent cells in the ovary/testis into haploid sex cells
39
Which one is a longer process (meiosis or mitosis)?
meiosis
40
how much time on average does a somatic cell mitosis happen?
12-24 hours
41
How much time for meiosis?
>48 days
42
How many division cycles does meiosis have?
2 division cycles
43
What is the result after Meiosis I?
results in 2 daughter cells
44
What is the result after Meiosis II?
results in 4 daughter cells
45
What is smt important to note b/w meiosis I and II?
after the cytokinesis in meiosis I, there is NO FURTHER DNA REPLICATION so NO interphase (go directly to Meiosis II, do not pass thru Interphase, do not replicate DNA)
46
Name all the steps in Meiosis I
Prophase I Metaphase I Anaphase I Telophase I Cytokinesis (2 daughter cells)
47
Name all the steps in Meiosis II
Prophase II Metaphase II Anaphase II Telophase II Cytokinesis (4 daughter cells)
48
Like mitosis, meiosis 1 is preceded by interphase, what happens during this phase?
G1 phase, S phase, G2 phase  duplication of chromosomes  2 chromatids held together by centromeres  centrioles also replicate (form centrosome)
49
What happens in Prophase I?
(similar to mitosis) NND/SAK/CS NND: Nucleolus and Nuclear membrane disappear SAK: Spindle attached to kinetochore CS: Centrioles continue sperating
50
What is different than mitosis?
The homologous pairs LINE UP with other homologous pairs
51
This line up with other homologous pairs forms what?
Tetrads
52
So what happens in Prophase I?
the formation of Tetrads (homologous chromosomes pair up)
53
What is called the process where homologous chromosomes come together is?
Synapsis (a process where a pair of homologous chromosomes held tightly together by proteins & CROSSING OVER occurs)
54
What does crossing-over produce?
it produced new gene combinations
55
TRUE OR FALSE: paired homologous chromosomes exchange genetic material between sister chromatids
FALSE: b/w NON sister chromatids
56
What does this mean?
chromatid from mom crosses over with chromatid from dad --> chromatid from mom does NOT cross over with sister chromatid from mom
57
So what is crossing-over?
Exchange of genetic material with an equivalent part of a chromatid from the other homologous chromosome (mom & dad, not mom & mom)
58
Crossing-over occurs during what phase?
Prophase I
59
What is the end result?
the chromosomes will have the same number of genes but the *sister chromatids are NO LONGER IDENTICAL* (+ contain parts from BOTH mom& dad now) (+ different alleles)
60
TRUE OR FALSE: Crossing over occurs at a specific point on a chromosome.
FALSE it can occur at any point
61
Why is this great?
b/c it introduces variation
62
Let's recap, what happens during Prophase I?
(similar to mitosis) NND/SAK/CS/HPT NND: Nucleolus and Nuclear membrane disappear SAK: Spindle attached to kinetochore CS: Centrioles continue separating HPT: Homologous pairs line up forming Tetrads
63
What comes after Prophase I?
Metaphase I
64
What happens during Metaphase I?
Spindles move Tetrads to cell midline (metaphase plate) Tetrads -> line up as homologous pairs (4 chromatids, NOT as 2 identical sister chromatids)
65
State the main difference between Metaphase in Mitosis and Metaphase I in meiosis
Metaphase Mitosis: - line up in a single file (kinetochores are attached to opposite poles of a single chromosome (2 sister chromatids) Metaphase I Meiosis: - chromosome line up as homologous pairs (TETRADS)
66
What happens during Anaphase I?
Homologous pairs segregate (set apart/split up)
67
Are the chromatids attached or separated?
Chromatids remain attached!
68
What does this mean then? Homologous pairs segregate
– Both copies of a homologous pair go to one end of cell – Both copies of the other go to the opposite end
69
State the main difference between Anaphase in Mitosis and Anaphase I in meiosis
Anaphase Mitosis: Centromere breaks sister chromatids separated (+ Each pole gets 1 copy of each single chromosome (1 sister chromatid) The daughter cell remains Diploid (2n) Has 2 different chromosomes) Anaphase I Meiosis: Homologous chromosomes separate this is called segregation Each pole gets 1 double / replicated chromosome (pair of chromatids) Diploid  haploid (n) Has 1 chromosome only
70
What comes after Anaphase I?
Telophase I
71
Name all the 4 things that happen during Telophase I:
COE, CAC, NMC, NR COE: chromosomes drawn to opposite ends of cell CAC: chromatids still attached by centromeres NMC: nuclear membrane surrounds chromosomes NR: Nucleoli reappear
72
What comes after Telophase I?
Cytokinesis
73
What is the result after cytokinesis?
Each daughter cell has both copies of one of each kind of chromosome (Reduced from 2n to n at this point => daughter cells are haploid & genetically different)
74
What is the conclusion at the end of Meiosis I?
Have 2 daughter cells (genetically different) - CHROMOSOME # IS HALVED (1n )!
75
Is there a DNA replication b/w the end of meiosis I and the beginning of meiosis II?
NO, CHROMOSOME REPLICATION
76
Main result/objective for meiosis II:
to distribute the copies of each chromosome into separate cells = separate sister chromatids
77
Name all the steps for meiosis II
Prophase II – Metaphase II – Anaphase II – Telophase II with cytokinesis at the end
78
Can we say that meiosis II and mitosis are similar?
YES, Meiosis II is very similar to Mitosis (without interphase / DNA replication)
79
Name all 3 things happening in Prophase II
NMND/SAK/CDS NMND: Nuclear membrane & nucleoli disappear SAK: Spindles attach to kinetochore CDS: Centrosomes duplicate and separate
80
What happens in Metaphase II
- attached chromatids ( ) line up on the midline of cell
81
Are the sister chromatids identical? why?
NOT IDENTICAL b/c of the crossing over in Prophase I
82
What happens in Anaphase II?
- centromeres break - chromosomes are drawn to opposite ends of the cell
83
What happens in Telophase II?
- Chromosomes are drawn to opposite ends of the cell – Nuclear membrane & nucleoli form
84
RESULT of Cytokinesis at the end
Each cell divides giving a total of 4 (4 haploid daughter cells genetically unique!!)
85
How many chromosomes does each cell have?
– Each cell now has 1 chromosome rather than the 2 the original cell had (Original parent cell = 2n Each Daughter cell = n)
86
general questions: Does mitosis or Meiosis increase genetic variation?
Meiosis
87
Name 3 mechanisms that contribute to genetic variation
1. Crossing over (during prophase 2. Independent assortment of chromosomes (during metaphase 3. Random fertilization (during zygote formation/conception)
88
Why does Crossing over help with genetic variation?
b/c it produces recombinant chromosomes (combines genes inherited from each parent)
89
How does an Independent assortment of chromosomes help with genetic variation?
Each pair of chromosomes sorts maternal and paternal homologues into daughter cells independently of the other pairs in meiosis I (Fun fact: For humans, there are more than 8.4 million possible combinations of chromosomes)
90
How does Random Fertilization help with genetic variation?
* any sperm can fuse with any ovum (unfertilized egg)
91
What is Evolutionary Significance?
Populations evolve through differential reproductive success of its variant members
92
Why is natural selection important?
Natural selection results in the accumulation of genetic variations favored by the environment + (Different combinations of alleles (sex) may work better than others in certain environments)
93
Difference b/w Mutation and sexual reproduction?
Mutation = original source of different alleles AND SEXUAL Reproduction= alleles mixed & matched during meiosis

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