Cell Division and Inheritance Pt. 2 Final

Question 1

What are some exceptions to Mendel’s principles?

Answer 1

Codominance
incomplete dominance
Neither dominant nor recessive
Multiple alleles
Many genes exist in several different forms and are therefore said to have multiple alleles
Genes with more than two alleles are said to have multiple alleles
Polygenic traits
Many traits are produced by the interaction of several genes, traits controlled by two or more genes are polygenic

Question 2

Does the environment have a role in how genes determine traits?

Answer 2

Phenotype of an organism is only partly determined by its genotype, partially determined by environment
Environmental conditions can affect gene expression and influence genetically determined traits

Question 3

zygote

Answer 3

a fertilized egg

Question 4

How many sets of genes are found in most adult organisms cells?

Answer 4

2

Question 5

How is meiosis different from mitosis?

Answer 5

Mitosis
2 cells made
Final products s2 sets of chromosomes
Diploid (46)
Healing, growth, replace worn out cells
All identical

Meiosis
4 cells made
1 set of chromosomes (half the chromosomes
Haploid (23)
Makes gametes
Sperm and eggs
Chromosomes have crossing over → recombination
Each cell is unique

Question 6

How can two alleles from different genes be inherited together?

Answer 6

Alleles of different genes tend to be inherited together from one generation to the next when those genes are located on the same chromosome

Question 7

Homologous chromosomes

Answer 7

Pair of chromosomes (maternal and paternal) that are similar in shape and size.
Homologous pairs (tetrads) carry GENES controlling the SAME inherited traits.
Each locus (position of a gene) is in the same position on homologues.
Humans have 23 pairs of homologous chromosomes:

Question 8

Diploid

Answer 8

A cell that contains both sets of homologous chromosomes (2n)

Question 9

haploid

Answer 9

Cells that contain only a single set of chromosomes, and therefore a single set of genes (1n)

Question 10

Meiosis

Answer 10

A process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell
The form of cell division by which GAMETES, with HALF the number of CHROMOSOMES, are produced.
DIPLOID (2n) → HAPLOID (n)
Meiosis is SEXUAL reproduction.
TWO divisions (MEIOSIS I and MEIOSIS II)
Sex cells divide to produce GAMETES (sperm or egg).
Gametes have HALF the # of chromosomes.
Occurs only in GONADS (testes or ovaries).
Male: SPERMATOGENESIS -sperm
Female: OOGENESIS - egg or ova
Yields nonidentical daughter cells

Question 11

spermatogenesis

Answer 11

Makes four sperm cells

Question 12

oogenesis

Answer 12

makes one egg, other three are polar bodies which die

Question 13

meiosis interphase

Answer 13

Similar to mitosis interphase.
CHROMOSOMES (DNA) replicate in the S phase
Each duplicated chromosome consist of two identical SISTER CHROMATIDS attached at their CENTROMERES.
CENTRIOLE pairs also replicate
Nucleus and nucleolus visible.

Question 14

Meiosis I (four phases)

Answer 14

Prophase I
Metaphase I
Anaphase I
Telophase I.
cytokinesis

Question 15

crossing over

Answer 15

Crossing over may occur between non-sister chromatids at sites called chiasmata, segments of nonsister chromatids break and reattach to the other chromatid chromosomes touch each other and exchange genes
Causes Genetic Recombination

Question 16

prophase 1

Answer 16

Longest and most complex phase (90%).
Nucleus and nucleolus disappear
Spindle forms
Chromosomes condense.
Synapsis occurs - Homologous chromosomes come together
to form a tetrad.
Tetrad is two chromosomes or four chromatids (sister and non-sister chromatids)
Crossing over occurs

Question 17

Metaphase I

Answer 17

Shortest phase, Tetrads (pairs of homologous chromosomes) line up across the center of the cell.
Independent assortment occurs – chromosomes line up randomly

Question 18

Anaphase 1

Answer 18

Homologous chromosomes separate and move towards the poles.
Sister chromatids remain attached at their centromeres.
Spindle fibers pull each homologous chromosome pair toward opposite ends of the cell

Question 19

Meiosis 2

Answer 19

No Interphase II or very short
No DNA Replication
Remember: Meiosis II is similar to mitosis

Question 20

telophase 1

Answer 20

Each pole now has haploid (1n) set of chromosomes.
A nuclear membrane forms around each cluster of chromosomes
Cytokinesis occurs and two haploid daughter cells are formed.

Question 21

prophase 2

Answer 21

Same as Prophase in mitosis
Nucleus & nucleolus disappear
Chromosomes condense
Spindle forms

Question 22

metaphase 2

Answer 22

Same as Metaphase in mitosis
Chromosomes line up

Question 23

anaphase 2

Answer 23

Sister chromatids separate.

Question 24

telophase 2

Answer 24

Same as Telophase in mitosis.
Nuclei and Nucleoli reform, spindle disappears
CYTOKINESIS occurs.
Remember: FOUR HAPLOID DAUGHTER cells are produced.
Called GAMETES (eggs and sperm)
1n chromosomes, 24 instead of 48

Question 25

variation

Answer 25

Also known as GENETIC RECOMBINATION
Important to population as the raw material for NATURAL SELECTION.
All organisms are NOT alike
Strongest “most fit” survive to reproduce & pass on traits

Question 26

3 sources of genetic recombination or variation?

Answer 26

CROSSING OVER (prophase I)
INDEPENDENT ASSORTMENT (metaphase I)
RANDOM FERTILIZATION

Question 27

karyotype

Answer 27

An organized picture of the chromosomes of a human arranged in pairs by size from largest to smallest.
Pairs 1-22 called AUTOSOMES
Last pair are SEX CHROMOSOMES

Question 28

fertilization

Answer 28

fusion of a sperm and egg to form a zygote