meiosis Flashcards
(104 cards)
1
Q
what happens in Interphase I? (2)
A
DNA is in loose form chromatin
All organelles and DNA get copied
2
Q
Prophase I (2)
A
Chromatin condenses
homologues come together (synapsis) in pairs called tetrads
chiasmata
3
Q
metaphase I
A
homologues line up at metaphase plate with the help of kinetochore microtubules
4
Q
anaphase i
A
homologous pairs get separated and pulled to opposite poles
5
Q
telophase I (4)
A
nuclear envelope reforms
spindle apparatus breaks up
nucleolus reappears
DNA loosens into chromatin
6
Q
cytokinesis I
A
cytoplasm splits resulting in two different daughter cells, each contain one of the homologues
7
Q
prophase II (3)
A
nuclear envelope breaks up
spindle apparatus forms and attached to sister chromatids
nucleolus disappears
8
Q
metaphase II
A
sister chromatids line up at metaphase plate
9
Q
anaphase II
A
sister chromatids separate at the centromere and move toward opposite poles
10
Q
telophase II (4)
A
nuclear envelope reforms
spindle apparatus breaks up
nucleolus reappears
DNA loosens into chromatin
11
Q
cytokinesis II
A
cytoplasm splits resulting in 4 different haploid daughter cells
12
Q
what is the units of inheritance onto offspring called?
A
genes
13
Q
where are genes located?
A
chromosomes
14
Q
what are genes made up of?
A
DNA
15
Q
what class of biomolecules does DNA belong to?
A
nucleic acids/ polynucleotide
16
Q
monomers of nucleic acids
A
nucleotides
17
Q
3 parts of nucleotides of DNA
A
Nitrogenous base, pentose sugar, phosphate group
18
Q
what does the N-base connect directly to?
A
phosphate group
19
Q
2 types of nucleic acids
A
DNA and Rna
20
Q
what do DNA and RNA enable organisms to do?
A
reproduce their components from one generation to the next
21
Q
two families in n-bases
A
purine and pyrimidines
22
Q
which n base family is bigger?
A
purines w/ 6 membered ring fused to 5 membered ring compared to 6 membered rings of pyrimidines
23
Q
types of purines
A
adenine and guanine
24
Q
members of pyrimidine family
A
DNA - cytosine, thymine
RNA - cytosine, uracil
25
what does adenine bond to?
thymine with 2 bonds between them
26
what does cytosine bond to?
guanine with 3 bonds between them
27
pentose sugar in DNA
deoxyribose
28
pentose sugar in RNA
ribose
29
difference between pentose sugar in DNA and RNA
deoxyribose lacks an oxygen atom on number 2 carbon
30
transmission of traits from one generation to the next
heredity
31
variation
changes from offspring to siblings
32
genetics
study of heredity and variation
33
number of chromosomes in human body cells
46 chromosomes in somatic cells
34
number of chromosomes in reproductive cells
23 chromosomes in gametes
35
how many genes on 46 chromosomes total?
20-25,000 genes
36
what does each chromosome consist of?
single long DNA molecule - has 100-1,000 of genes on it
37
what is the gene's locus
specific location on the chromosome
38
plural of locus
loci
39
what does our genes program?
the specific traits that emerge as we develop from fertilized eggs to adults
40
what information do genes contain?
info of all the traits of the body
41
why does the DNA rely on the mRNA?
it's too big to exit the nucleus, so it relies on the mRNA to transcribe/ carry out DNA's message out of the nucleus
42
what does the mRNA do after exiting the nucleus?
arrives at a ribosome where the message gets translated into the making of a polypeptide
43
asexual reproduction occurs more often with?
unicellular organisms
44
how do some multicellular organisms asexually reproduce (along with unicellular)?
budding
45
how are buds derived?
by mitosis - not meiosis, therefore the offspring are identical to the parent assuming no mutation
46
what does asexual reproduction bring about?
clones of genetically identical individuals
47
how does sexual reproduction relate to variation/diversity?
results in greater genetic variation because unique combinations of genes come from both parents
48
what is sexual reproduction the result of?
gametes coming together that were formed during meiosis
49
what does the life cycle of an organism follow?
the reproductive stages of an organism from generation to generation
50
how do chromosomes differ? (3)
by their lengths, location of their centromeres, and by their distinctive banding patterns when stained
51
although humans have 46 chromosomes, how many pairs do we have?
23 pairs - 2 each kind. one from maternal and one from paternal
52
what is it called when chromosomes are arranged in pairs starting with the longest?
karyotype
53
what are chromosomes that carry the same traits called? (4)
homologues
homologous pairs
homologous chromosomes
tetrads
54
different stages of "chromosomes"
chromosome -> 2 sister chromatids -> tetrads
55
what type of genes do homologous pairs carry?
same genes at the same loci
56
how do traits show up in chromosomes?
different version called alleles
57
what is the exception to alleles?
X and Y chromosomes (sex chromosomes)
58
female homologous chromosomes
XX
59
male homologous chromosomes
XY
60
why do we have homologous pairs of chromosomes?
we inherit 1 chromosome from each parent, so altogether we inherit 23 chromosomes from mom and 23 from dad
61
what do each egg/sperm cell contain?
22 autosomes and either an X or a Y for a total sum of 23 chromosomes
62
what type of cells are gametes?
haploid (1n)
63
what happens in fertilization?
2 haploids come together to form a zygote that is diploid (2n)
64
what happens once the zygote forms?
mitosis/cleavage occurs to allow the offspring to grow and develop
65
what are the only cells in the body not made by mitosis?
gametes that are made in the gonads by meiosis
66
2 types of meiosis
spermatogenesis
oogenesis
67
are all life on earth separated into 1n and 2n?
no, fungi and some algae are different, their multicellular body cells and agmates are already in 1n state, so via mitosis they are ready to fertilize/form a zygote - the 2n state temporarily
68
what do fungi need to do since their body cells exist normally as multicellular haploids?
halve their chromosome number and this is accomplished by meiosis
69
animal multicellualr form
2n
70
animal gamete form
1n
71
fungi multicellular form
1n
72
fungi gamete form
1n
73
if you want to take a 2n down to 1n, what is this process called?
meiosis
74
what is cloning/making more of whatever the cell type happens to be?
mitosis
75
examples of mitosis in haploid and dipold cells
haploid cells copy themselves, divide, or make more haploids
diploid cells copy themselves, divide, and make more diploids
76
what does meiosis consist of?
meiosis I and meiosis II
2 cell divisions resulting in 4 daughter cells
77
where in the cell cycle have chromsomes replicated?
s phase of interphase
78
what are the different terms to call these x shaped structures?
sister chromatids, duplicated/replicated chromosomes
79
with meiosis, a replicated chromosomes stays nearby its matching replicated chromosomes in what stages?
prophase i, metaphase ii
80
what do you call 2 replicated chromosomes next to each other?
tetrads, homologues, homologous pairs/chromosomes
81
what do you call the process of the 2 X's coming together?
synapsis
82
since there are four chromatids, what is this called?
tetrads
83
when in meiosis does the exchange of genetic material called crossing over occur resulting in chiasma?
prophase i
84
what is the whole point of meiosis i?
separate homologous pairs
85
what is the whole point of meiosis ii?
separate sister chromatids
86
is meiosis i or meiosis ii more like mitosis?
meiosis ii, both separate sister chromatids
87
DNA replication occurs in what part of the cell cycle and how many times in mitosis?
S phase of interphase - once
88
DNA replication occurs in what part of the cell cycle and how many times in meiosis?
S phase of interphase - once
89
number of cell divisions in mitosis?
1
90
number of cell divisions in meiosis?
2
91
does synapsis occur and if so when in mitosis?
no
92
does synapsis occur and if so when in meiosis?
yes - prophase I
93
what is number of daughter cells and are they different or identical in mitosis?
2 - identical
94
what is number of daughter cells and are they different or identical in meiosis?
4 - different
95
role of mitosis
growth and tissue repair
96
role of meiosis
make gametes
97
why are offspring of sexually reproducing organisms not genetically the same? (3)
Independent Assortment
Crossing Over
Random Fertilization
98
what is Independent Assortment?
Law of Assortment - when homologues line up at the equator of the cell in metaphase I, it is random ("independent") event for each homologous pair
99
what is the number of possible combinations due to the Law of Assortment?
2^n, where n is the haploid number
100
how many possible different gametes are there in humans?
2^23 ~ 8 million
101
what is crossing over?
occurs during prophase i of meiosis when homologues come together in a process called synapses to form pairs called tetrads. then nonsister chromatids trade places - resulting regions are called chiasmata
102
on average, how many crossing over events are there?
2-3 per homologous pair
103
what is random fertilization?
there would be 64 trillion possible combinations of chromosomes solely looking at the 8 million possible different ovules and 8 million possible different sperms not counting crossing over
104
what process creates the greatest number of new genetic combinations?
mutations
