cell division an inheritance part 2

Question 1

homologous pairs

Answer 1

matching genes - one from female parent and one from male parents

Question 1

alleles

Answer 1

different genes for the same trait

Question 2

amount of chromosomes in cells

Answer 2

Ex. humans have 46 chromosomes or 23 pairs
One set from dad - 23 in sperm
One set from mom - 23 in egg

Question 3

Genotype

Answer 3

Combination of genes an organism has (actual gene makeup)

Question 4

phenotype

Answer 4

physical appearance resulting from gene makeup

Question 5

Where does an organism get its unique characteristics?

Answer 5

Organisms inherit their set of characteristics from their parents or parent
An individual’s characteristics are determined by factors that are passed from one parental generation to the next

Question 6

How are different forms of a gene distributed to offspring?

Answer 6

During gamete formation, the alleles for each gene segregate from each other, so that each gamete carries only one allele for each gene

Question 7

How to allele segregate when more than one gene is involved?

Answer 7

Independent assort, genes for different traits segregate independently during the formation of gametes

Question 8

What did Mendel contribute to our understanding of genetics? (4 concepts!)

Answer 8

Traits are determined by genes, which are passed from parent to offspring
Principle of dominance, some alleles are dominant and others are recessive
Each adult has two copies of each gene–one from each parent
Segregation, During gamete formation, the alleles for each gene segregate from each other, so that each game carries only one allele for each gene
Independent assortment, genes for different traits can segregate independently during the formation of gametes, inheritance of one trait has no effect on the inheritance of another trait

Question 9

What are some exceptions to Mendel’s principles?

Answer 9

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 10

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

Answer 10

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 11

zygote

Answer 11

a fertilized egg

Question 12

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

Answer 12

2

Question 13

How is meiosis different from mitosis?

Answer 13

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 14

How can two alleles from different genes be inherited together?

Answer 14

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 15

Homologous chromosomes

Answer 15

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 16

Diploid

Answer 16

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

Question 17

haploid

Answer 17

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

Question 18

Meiosis

Answer 18

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 19

spermatogenesis

Answer 19

Makes four sperm cells

Question 20

oogenesis

Answer 20

makes one egg, other three are polar bodies which die

Question 21

meiosis interphase

Answer 21

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 22

Meiosis I (four phases)

Answer 22

Prophase I
Metaphase I
Anaphase I
Telophase I.
cytokinesis

Question 23

crossing over

Answer 23

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 24

prophase 1

Answer 24

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 25

Metaphase I

Answer 25

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

Question 26

Anaphase 1

Answer 26

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 27

telophase 1

Answer 27

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 28

Meiosis 2

Answer 28

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

Question 29

prophase 2

Answer 29

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

Question 30

metaphase 2

Answer 30

Same as Metaphase in mitosis
Chromosomes line up

Question 31

anaphase 2

Answer 31

Sister chromatids separate.

Question 32

telophase 2

Answer 32

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 33

variation

Answer 33

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 34

3 sources of genetic recombination or variation?

Answer 34

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

Question 35

karyotype

Answer 35

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 36

fertilization

Answer 36

fusion of a sperm and egg to form a zygote