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Meiosis Flashcards

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1
Q

Hereditary

A

the transmission of treats form one generation to the next

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2
Q

variation

A

differences in appearances the offspring show from parents and siblings

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3
Q

genetics

A

the scientific study of hereditary and variation

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4
Q

genes

A

hereditary units
- offsprings acquire genes form parents by inheriting chromosomes
- made up of DNA
-passed via gametes

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5
Q

gametes

A

reproductive cells (seems and eggs)

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6
Q

fertilization

A

sperm and eggs unite, passing on genes of both parents to their offspring

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7
Q

somatic cells

A

46 chromosomes, all cells of body except games and their precursors
- 23 pairs, 1 from mother and 1 from father

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8
Q

locus

A

each gene’s specific position on a certain chromosome

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9
Q

asexual reproduction

A

single individual passes Gennes to its offspring without fusion of gametes

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10
Q

sexual reproduction

A

two parents give rise to offspring that have unique combinations of genes inherited form the two parents

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11
Q

clone

A

a group of genetically identical individuals form the same parent (asexual)

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12
Q

life cycle

A

the generation to generation sequence of stages in reproductive history of an organism

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13
Q

karyotype

A

an ordered display of the pairs of chromosomes from a cell

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14
Q

homologous chromosomes/homologs

A

two chromosomes in each pair
- same length and shape and carry genes controlling same inherited characters
- each pair includes one chromosome form each parent

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15
Q

sex chromosomes

A

X and Y
- females: XX, males: XY

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16
Q

autosomes

A

remaining 22 pairs of chromosomes

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17
Q

a diploid cell (2n)

A

has two sets of chromosomes
-for humans the diploid number is 46 (2n=46)

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18
Q

in DNA synthesis each chromosome is…

A

replicated
- each chromosome consists of two identical sister chromatids

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19
Q

haploid (n)

A

a single set of chromosomes (a gamete)
- human haploid number is 23
- 23 consists of 22 autosomes and a single sex chromosome (egg is X, sperm is X or Y)

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20
Q

zygote

A

fertilized egg, has one set of chromosomes from each parent
- produces somatic cells by mitosis and develops into an adult

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21
Q

Ovaries and testes produce…

A

haploid games

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22
Q

gametes are the only types of human cells produced by…

A

meiosis rather than mitosis

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23
Q

meiosis results in

A

one set of chromosomes in each gamete

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24
Q

fertilization and meiosis alternate in…

A

sexual life cycles to maintain the chromosome number

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25
gametes fuse to form a
diploid zygote that divides by mitosis and develop into a multicellular organism
26
mitosis and meiosis are preceded by...
the duplication of chromosomes
27
meiosis has two sets of cell division:
meiosis I and meiosis II - result in 4 daughter cells; each has half as many chromosomes as the parent cell
28
stages of meiosis
homologs chromosomes duplicated = sister chromatids, may have different versions of genes (alleles)
29
Meiosis 1
homologous pairs separate
30
Meiosis II
sister chromatids separate - 4 new haploid cells
31
prophase I
homologous chromosomes pair up and align, crossing over happens, forms chiasmata - forms recombinant chromatids
32
crossing over
non-sister chromatids exchange DNA segments
33
chiasmata
each homologs pair has 1 or more X-shaped regions; exist where crossing over happens
34
synopsis during prophase I
- synaptonomal complex - DNA of mom and dad chromatid are broken at matching points - then crossing over happens
35
synaptonomal complex
zipper-like structure that forms when homologous pair up
36
Mitosis summary
conserves number of chromosome sets, producing genetically identical
37
Meiosis summary
chromosomes sets from diploid to haploid; cells differ from each other and parent - has 2 divisions after replication - meiosis I: synapsis and crossing over in prophase I, alignment of homologous at metaphase plate, separation of homologs during anaphase I
38
mutations are the source...
of genetic diversity, create different version of genes called alleles - reshuffling of alleles during sexual reproduction produces genetic diversity
39
three mechanisms contribute to genetic variation:
- independent assortment of chromosomes - crossing over - random fertilizations
40
independent assortment of chromosomes
homologous pairs orient randomly at metaphase I -> each pair sorts mom and dad homologs into daughter cells independently of the other pairs - possible combos = 2n = 8.4 million
41
random fertilization
any sperm can confuse with any egg; 70 trillion possible combos
42
blending hypothesis
idea that genetic material from the two parents blend together (WRONG)
43
particulate hypothesis
idea that parents pass on discrete heritable units (genes) - mendel confirmed with garden pears
44
Mendel discovered the basic principles of hereditary by...
Breeding garden peas in carefully planned experiments (stamens + eggs) - worked with peas because because of characters (distinct heritable features) and traits (character variants) - could control mating
45
two distinct alternative forms of mating
- true breeding - hybridization
46
true-breeding
plants that produce offspring of the same variety when they self-pollinate
47
hybridization
mated two contrasting, true-breeding varieties
48
generation names
P generation (true breeding parents), F1 generation (the hybrid off spring of P generation) and the F2 generation (when F1 self pollinate or cross pollinate)
49
Results of Mendels experiment
all F1 were purple, F2: 3/4 purple + 1/4 white (3:1 ratio) - In F1 plants, the heritable factor for white flowers were hidden/masked by purple flower factor - Mendel saw same thing in 6 other pea plant characters
50
purple flower and white flower
purple: dominant trait white: recessive trait
51
Mendel's Model explains 3:1 ratio in F2 offspring: 1st statement
1st: alternative versions of genes account for variations in inherited characters -alleles at specific locus
52
Mendel's Model explains 3:1 ratio in F2 offspring: 2nd statement
for each character, an organism inherits two alleles, one from each parent
53
Mendel's Model explains 3:1 ratio in F2 offspring: 3rd statement
if the two alleles at a locus differ, then one (the dominant allele) determines the organism's appearance, and the other (the recessive trait) has no noticeable effects in appearance
54
Mendel's Model explains 3:1 ratio in F2 offspring: 4th statement
law of segregation - the two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes
55
Punnett Square
predict results of genetic cross - a capital letter represents a dominant allele, lowercase represents a recessive allele
56
homozygous
two identical alleles (PP or pp) - true breeding
57
heterozygous
two different alleles (Pp)
58
phenotype and genotype
phenotype: physical appearance genotype: genetic makeup
59
How can we tell the genotype of an individual with the dominant phenotype?
testcross: breeding mystery individual with a homozygous recessive individual (pp)
60
any gamete produced by an individual heterozygous for a trait has a...
50% probability of carrying the dominant and 50% of carrying the recessive

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