Meiosis Flashcards
Chromosomes
the carriers of genes, which are located in specific positions
Homologous Chromosomes
chromosomes that are identical (same centromere, same location, and genes)
Where do homologous chromosomes come from?
one from each parent —> mom and dad
The diploid cells of most adult organisms contain 2 complete sets of _____ _____ and two complete sets of ______
inherited chromosomes; genes
The gametes of sexually reproducing organisms are ____
haploid
Meiosis
the formation of gametes
a process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell
What is the end result of meiosis
egg and sperm cells
Gametes
sex cells (egg and sperm )
Egg cells are ____ reproductive cells
female
Sperm cells are ____ reproductive cells
male
How many chromosomes do gametes have?
23
Do gametes go through mitosis
no bc they have half the amount of chromosomes
Gonad
reproductive organs
haploid
(n) 1 set of chromosomes
Diploid
(2n) 2 sets of chromosomes
What does the n in hiploid and diploid cells represent
a single set of chromosomes found in a sperm or egg cell
Female gonad
ovary
Male gonad
testes
How many stages does meiosis have?
DOS
What happens before meiosis
Interphase
Is interphase a step in meiosis?
no
How many steps does interphase have?
3
What are the steps of interphase
1) G₁
2) S
3) G₂
G₁ is aka
Gap 1
S is aka
synthesis
G₂ is aka
Gap 2
Gap 1
basic growth of proteins, organelles, etc. Cell gets bigger and undergoes chemical processes
Synthesis
where we copy genetic material. (duplicate chromosomes)
Begins with 46 chromosomes (46 chromatids) –> duplicates into 46 chromosomes (92 CHROMATIDS)
Gap 2 is aka
the mitosis prep stage
Gap 2
duplicate centrosomes and centrioles (CENTRIOLES IN ANIMAL CELLS ONLY)
What is the shortest phase of interphase
Gap 2
Gap 1 and Gap 2 are periods of…
intense growth and activity
What are the two stages of meiosis?
Meiosis I and Meiosis II
How do we count chromosomes
by the amount of centromeres
How many times do cells divide in meiosis
twice
Why do cells in meiosis divide twice
to get from 46 chromosomes (92 chromatids) to 46 chromosomes (46 chromatids) to 23 chromosomes (23 chromatids) [23 IS THE AMT OF CHROMOSOMES GAMETES HAVE]
Meiosis I
split into 46 chromosomes (46 chromatids) from 46 chromosomes (92 chromatids)
How many steps does Meiosis I have?
CINCO
What are the five steps of Meiosis I
PI, MI, AI, TI, Cytokinesis
PI (Prophase 1) has ___ steps
2
What is the first step of PI
Synapsis
Synapsis
the replicated chromosomes pair with their corresponding homologous chromosomes
What is formed in synapsis
tetrads
Tetrad
structure containing 4 chromatids (2 corresponding homologous chromosomes)
What is the second step of PI
Crossing over
Crossing over
The chromatids of the homologous chromosomes cross over one another and the crossed sections are exchanged
How many times does crossing over occur?
about 2-3 times
What does crossing over create?
Recombinant chromosomes
Recombinant Chromosomes
new combinations of alleles formed from the switched genes (parts of chromosomes)
What is the second step of Meiosis 1
MI
What happens in MI
The paired homologous chromosomes line up across the center of the cell in two lines because they are pairs
What is the sub step between MI and AI
Independent Assortment
Independent Assortment
the law that states that each homologous chromosome has an equal chance of assorting to either side
What is the step after Independent Assortment?
AI
What happens in AI
spindle fibers pull each homologous chromosome pair towards opposite ends of the cell
What is the step after AI
TI
What happens in TI
- Reform nuclear envelopes and nucleolus
- the spindle fibers break down (hydrolyze)
What happens after TI
cytokinesis
Cytokinesis
splits cell into two haploid daughter cells
At the end of Meiosis 1 the chromosomes are still ____
double
What happens after Meiosis 1
G₁ and G₂
Does interphase occur between Meiosis 1 and Meiosis 2?
no, bc there is no synthesis
What happens after G₁ and G₂?
Meiosis II
Meiosis II
splits 46 chromosomes (46 chromatids) into 23 chromosomes (23 chromatids)
How many steps are in Meiosis II and what are they
P II, M II, A II, T II
All the steps in Meiosis are…
the same as mitosis
What is the result of Meiosis II
4 haploid daughter cells
Zygote
fertilized (by sperm) egg
Gene Mapping
the process of locating genes on a chromosome
What are the measurements used in Gene Mapping?
mapping units
How is gene mapping determined?
determined by the percentage of crossing over (higher chance of crossing over when genes are far, smaller chance if genes are close)
Gene Linkage
If two genes are located close to each other on a chromosome then they are linked and usually do not assort independently
There are ______ of genes per chromosome
thousands
Mendel had knowledge of chromosomes (True or False)
False
heredity