Chapter 2 Flashcards
Define mitosis
Cell division to produce new somatic cells
Define somatic cells
All nonreproductive cells in the body
Define meiosis
Cell division to produce gametes
Define gametes
Reproductive cells
What is the nucleus?
Organelle where DNA is held
What is the mitochondria
Produces ATP. Has its own DNA.
What is the Rough ER
Makes proteins with help of ribosomes
What is the cytoskeleton
Protein fibers that give cells their shape
What is the cytoplasm
Space outside of the nucleus - this includes all the other organelles
What is the cytosol
The gooey space inside the cell
Define a zygote
A fertilized egg. This is how all humans start out as.
What are the 5 stages of the cell cycle?
1) G1 (gap1)
2) G0 (dormancy)
3) S1 (synthesis phase)
4) G2 (gap 2)
5) Mitosis
What is G1 phase?
Cell is born and grows
What is G0 phase?
Cell enters dormancy and stops growing/dividing. Commonly how neurons end up.
What is S1 phase?
Cell copies it’s chromosomes in preparation to divide
What is G2 phase?
Cell grows again to divide
What is Mitosis (general)
Multistep process where division takes place.
*Shortest stage
What are the stages of mitosis?
1) Prophase
2) Prometaphase
3) Metaphase
4) Anaphase
5) Telophase & Cytokinesis
When are chromosomes copied?
During the S-phase. All 46 chromosomes are copied.
Define sister chromatids
The 2 halves of the “X” copy of the chromosome. Genetically identical and held together by the centromere.
Define centromere
Central region that holds chromatids together
What is interphase?
Everything before mitosis
What is prophase?
Chromosomes condense and enter the cytosol
What is prometaphase?
Spindle fibers form and attach to chromosomes
What is metaphase?
Chromosomes line up in the center
What is anaphase?
Sister chromatids are split apart by spindle fibers
What is telophase?
Chromosomes reach end of the cell and new nuclei reform
What is cytokinesis?
Cell splits into 2.
Define disjunction?
Splitting of the junction - when sister chromatids are split apart in anaphase.
If the parent starts with 46 chromosomes in mitosis, how many chromosomes will the daughter cells get?
46 chromosomes. Parent and daughters are genetically identical.
Where is centromere on a metacentric chromosome?
Center. Makes a perfect “X”
Where is centromere on a submetacentric chromosome?
Slightly offset from the center. Has a p-arm and q-arm
Which is larger: the p-arm or q-arm?
q-arm is larger.
p-arm is smaller
Where is centromere on a acrocentric chromosome?
Centromere is close to the end.
Where is centromere on a telocentric chromosome?
Centromere is at the end.
What is a karyogram?
A visual image of each chromosome
What are the name of the gametes that meiosis creates?
Spermatozoa - male
Ova - female
Are humans diploid or haploid? define haploid and diploid.
Diploid
Diploid is 2 copies of each chromosomes
Haploid is 1 copy of each chromosome
How many chromosomes are in a diploid cell?
23 pairs, 46 total chromosomes
Define homologous chromosome
A pair of chromosomes that are similar - one came from mother, other from father
Are gametes haploid or diploid?
Haploid because they DO NOT have their homologous pair
Define biparental inheritance
An organism’s genetic material comes from 2 parents.
Define loci
The genetic location responsible for a particular trait BUT can contain different alleles.
What is an example of homologous pairs that aren’t truly identical
Blood antigen gene. Varientys of the blood antigen allele results in different blood types.
What does Meiosis I do? What does Meiosis II do?
Meiosis I - Separating homologous chromosomes
Meiosis II - Splitting sister chromatids
What happens before meiosis begins?
Germ cell duplicates it’s chromosomes.
What happens in Prophase I?
Homologous chromosomes assemble in pairs (XX). Spindle fibers attach to each homologous chromosome.
Define synapsis
Assembly of homolgoous chromosomes into pairs (XX)
AKA prophase
Define tetrad
4 sister chromatids adhered in pairs.
Define crossing over
DNA being swapped between homologous chromosomes.
When does crossing over occur?
Prophase I
What are the (3) benefits of crossing over?
-Generates more genetically diverse offspring
-Better mix of parental genes
-Generates new phenotypes and has adaptive potential.
Define chiasma
Point of contact between crossing chromosomes
Define recombinant chromatids
Chromatids that have partaken in crossing over
What happens in Metaphase I?
Homologous chromosomes line up in the center
What happens in Anaphase I?
Each homologous chromosome is pulled to the side.
DISJUNCTION
What happens in Telophase I / cytokinesis?
Chromosomes reach end of cell, new nuclei reform and cell splis in 2.
Whats the chromosome & chromatid count at the beginning and end of Meiosis I?
end of Meiosis II?
Beginning: 46 chromosome | 92 sister chromatids (2n cell)
End Meiosis I: 23 chromosomes | 46 sister chromatids (1n cell)
End Meiosis II: 23 chromosomes | 23 chromatids (1n cells)
What are the benefits of distinct gametes (3)?
- All offspring are unique and more likely to be adaptive to their environment
-Populations are more resistant to defective alleles
-Some alleles don’t get passed on
What processes allow for gametes to be distinct?
Independent assortment and crossing over
Define independent assortment
Homologous chromosome of either parent can be on the left or right in metaphase I
Define spermatogenesis
Production of spermatozoa - takes place in the testes
Define spermatogonium
Male germ cell.
What does spermatogonium undergo to make?
Undergoes interphase (G1, S, and G2 phases) to make a primary spermatocyte
Define a primary spermatocyte
matured spermatogonium that is ready to undergo meiosis I.
What does a primary spermatocyte produce?
2 secondary spermatocytes.
What does a secondary spermatocyte produce?
Undergoes meiosis II to create 2 immature spermatids
How many spermatids are produced from 1 spermatogonium?
4 spermatids
Define spermatids
An immature cell that is immotile and cannot fertilize the ovum.
Define spermiogenesis
Maturation process of spermatid into spermatozoa.
Forming of acrosome, flagella, and head.
Define:
a) acrosome
b) flagella
a) head of the spermatozoa, penetrates the egg and contains the chromatin
b) tail propeller to travel
Define oogenesis
Production of ova - taking place in the ovaries
Define oogonium
Female germ cell
What does the oogonium go through to create?
Goes through interphase (G1, S1, G2 phases) to create a primary oocyte.
What does the primary oocyte do?
Splits asymmetrically during Meiosis I to result in 1 secondary oocyte and 1 first polar body.
Why does the primary oocyte split asymmetrically?
One ova needs all the nutrients/cytoplasm it can get. Ensures a healthier zygote.
Define secondary oocyte
The bigger daughter cell that receives most of the cytoplasm and goes on to meiosis II.
Define polar body
The smaller daughter cell from either meiosis I or II and usually dies
What happens to the secondary oocyte?
Divides asymmetrically during meiosis II to create 1 ootid and a second polar body.
Define ootid
The bigger daughter cell resulting from meiosis II—an immature gamete.
Define ovum
Final female gamete - results from maturation of ootid.
When does oogenesis begin?
As a fetus. Oogenesis pauses in prophase I, before continuing after puberty and being completed only AFTER fertilization.
Who influences your offspring’s health?
Your mom. Your mother’s pregnancy influences your offsprings health due to oogenesis beginning in utero.
If an organism has 10 total chromosomes in its somatic cells, how many chromosomes would a 1n cell of that organism have?
5 chromosomes
If an organism had a total of 40 chromosomes in its somatic cells, how many chromosomes would a 2n cell of that organism have?
40 chromosomes
If an organism had 12 chromosomes in its ova, how many chromosomes would it have in a 2n cell?
24 chromosomes
Imagine diploid somatic (“body”) cell has 2n = 20 chromosomes. At the end of mitosis, each daughter cell would have ______ chromosomes. At the end of meiosis I, each daughter cell would have ______ chromosomes. At the end of meiosis II, each daughter cell would have ______ chromosomes.
20
10
10
