Bio Chp 4 - Genetics

Question 1

What is the process of mitosis?

Answer 1

This is the process whereby a eukaryotic cell separates the chromosomes into two identical sets into two separate nuclei.

Question 2

What is the process of cytokinesis?

Answer 2

This it the process whereby the cell divides the nuclei, cytoplasm, organelles, and cell membrane into two cells containing roughly equal shares of these cellular components.

Question 3

What do the combine of mitosis and cytokinesis define?

Answer 3

The so-called mitotic (M) phase. This apparently accounts for about 10% of the cell cycle.

Question 4

What is interphase?

Answer 4

Interphase is a much longer phase than the mitotic phase. This is where the cell prepares itself for division.

Question 5

How many phases define interphase?

Answer 5

There are three phases within interphase. 1) G1 (first gap) 2) S (synthesis) 3) G2 (second gap).

Question 6

What happens during interphase?

Answer 6

Throughout G1, S, and G2 the cell continues to grow by producing proteins and cytoplasmic organelles. But only during the S phase does the cell duplicate its chromosomes.

Question 7

What else duplicates besides the chromosomes during S-Phase?

Answer 7

The centrosome composed of centrioles and microtubules.

Question 8

What happens during prophase?

Answer 8

1) Chromatin condenses into chromsomes

2) Nucleolus disappears

Question 9

What happens during Prometaphase?

Answer 9

1) Nuclear membrane breaks down
2) Kinetochore microtubules invade nuclear space, and attach to kinetochores
3) Polar microtubules push against each other moving centrosomes apart

Question 10

What happens during metaphase?

Answer 10

Chromsomes line up along metaphase plate (imaginary plane)

Question 11

What happens during anaphase?

Answer 11

Chromosomes break at centromeres and sister chromatids move to opposite ends of the cell.

Question 12

What happens during Telophase?

Answer 12

1) Nuclear membrane reforms
2) Nucleoli reappear
3) Chromosomes unwind into chromatin

Question 13

What happens during cytokinesis?

Answer 13

Myosin II and actin filament ring contract to cleave cell in two at the so-called “cleavage furrow”

Question 14

What cells are produced by Meiosis?

Answer 14

The cells produced by meosis are gametes or spores.

Question 15

What are animal gametes called?

Answer 15

sperm and egg

Question 16

How does meiosis differ from mitosis?

Answer 16

1) The chromosomes in meiosis undergo a recombination which shuffles the genes to produce a different genetic code in each gamete. This happens during prophase portion of the meiosis cycle.
2) Meiosis is not a cyclic process. And it produces four genetically unique haploid cells compared with two genetically identical diploid cells of mitosis. Therefore, there are two prophases, metaphases, anaphases, and telophases.

Question 17

What is the gametic life cycle?

Answer 17

The species is diploid! The general principle is that a diploid zygote undergoes repeated cellular division by mitosis to grow into the organism. Then the stem cell’s of the dipload organism undergo meiosis to create haploid gametes. Haploid gametes fertilize each other to form a zygote.

Question 18

What is the zygotic life cycle?

Answer 18

The species is haploid! This stands in contrast to the gametic life cycle. Here the key difference is that the diploid zygote UNDERGOES MEIOSIS IMMEDIATELY. Then the haploid cells undergo repeated mitosis to create the organism. Two diploid gametes of different organisms fertilize each other into a haploid zygote, which them immediately undergoes meiosis. And the cycle is repeated.

Question 19

What organisms have a zygotic life cycle?

Answer 19

Fungi and protozoa are examples.

Question 20

What is a gene? What does it do?

Answer 20

It is the molecular unit of heredity. It codes for RNA and DNA. Not all stretches of DNA actually code for something.

Question 21

What is the genome?

Answer 21

The sum total of an organism’s hereditary information including coding and non-coding sequences. It can be DNA or RNA.

Question 22

What is a chromosome?

Answer 22

It is a packaging of DNA and protein. Essentially, the double helix of the DNA is wrapped around histones, which then are compacted into a need alternating structure. Which is then wrapped around further protein scaffolding which is yet wrapped again. And around this point, chromosomes appear as they do in metaphase in the “X” like structures we prototypically see. Generally, the less wrapped the DNA is the more actively it is being transcripted.

Question 23

What is a diploid organism?

Answer 23

It has two sets of chromosomes.

Question 24

What are the chromosomes of diploid organisms called?

Answer 24

They are called homologous chromosomes.

Question 25

How many copies of each gene do diploid organisms have?

Answer 25

One

Question 26

How many alleles of each gene do diploid organisms have?

Answer 26

They have two alleles. One on each chromosome.

Question 27

If a diploid organism has both alleles of a gene the same, what are they called?

Answer 27

homozygotes

Question 28

If a diploid organism has both alleles of a gene different, what are they called?

Answer 28

heterozygotes

Question 29

Who was Gregor Mendel?

Answer 29

He was an Austrian scientist (and friar) who gained posthumous fame for his discovery of the genetics of Mendelian inheritance. He lived 1822-1884.

Question 30

What is incomplete dominance?

Answer 30

This happens when the phenotype of the heterozygous genotype is distinct from and often intermediate to the phenotype of the homozygous genotypes. An example is a red/white flower cross. Where the result the heterozygous flower has a pinkish color.

Question 31

What is F1 in genetics?

Answer 31

It stands for filial 1. It is the first generation of offspring from distinctly different parental types.

Question 32

What is F2 in genetics?

Answer 32

This is the generation that results from crossbreeding only from the F1 generation.

Question 33

What is Mendel's principle of segregation?

Answer 33

It states that each parent carries two copies of the particles (genes) that determine a single trait. When gametes are formed, the two particles (alleles) separate, so that each gamete receives on copy.

Question 34

What is Mendel's principle of assortment?

Answer 34

The segregation of one pair of alleles is independent of the segregation of the other pair of alleles-- in the case of a two trait cross. For example, when a parent is heterzygous for both traits, then all four possible gametes have an EQUAL chance of forming. (There is no conditional probability). P(AB) = P(A)*P(B).

Question 35

While ignoring the process of crossing over during Meiosis, how many possible gametes are there for a human just based on chromosomes?

Answer 35

The two partners of a homologous chromosome are never genetically identical. The principle of independent assortment leads to the genesis of all possible chromosome combinations. 2 choices of chromosome. 23 chromosomes. 2^23 outcomes. So two parents can have 2^(23)*2^(23) = 2^46 ~ 64*10^12 different zygotes.

Question 36

For family tree analysis, how can we tell that a treat is recessive?

Answer 36

For a dominant trait, at least one parent of a child expressing the dominant trait, must also express the trait by the definition of dominance. If this is not true, then the trait must be recessive.

Question 37

How do you determine is a trait is autosomal or sex-linked?

Answer 37

The trait is autosomal if it affects roughly equal numbers of females and males. Most likely.

Question 38

How do we determine is a trait is sex linked?

Answer 38

1) Every affected male must have an affected mother. 2) Every daughter of an affected male must be affected.

Question 39

Do all genes have to have two alleles?

Answer 39

In fact, no. Genes can have multiple alleles and this can only be analyzed within populations.

Question 40

What is an example of a trait with multiple alleles?

Answer 40

AB0-bloodgroups. There are three alleles of the blood group gene, A, B, 0.

Question 41

How many phenotypes for bloodgroup are there?

Answer 41

There are four phenotypes: A-Antigen, B-Antigen, A and B-antigen, no antigen. These are denoted phenotype A, B, AB, and 0.

Question 42

How do the genes for bloodgroup interact?

Answer 42

The genes A, B are dominant over 0. And A, B are co-dominant themselves.

Question 43

What is an example of an X-linked genetic disorder/trait?

Answer 43

Haemophilia A is a recessive X-linked genetic disorder. It involves the lack of a functional clotting factor viii and represents 80% of haemophilia cases.

Question 44

Can the environment have an effect on phenotype?

Answer 44

Yes. For example, temperature can affect chemical activities that depend on kinetic energy of reacting substances. The Himalayan rabbit and Siam cat have temperature sensitive pigmentation.

Question 45

What is genomic imprinting?

Answer 45

It is an epigenetic process, that can involve DNA methylation and histone modulation. It achieves monoallelic gene expression without altering genetic sequence. The point is that the alleles inherited from one parent are silenced. And only the genes that the other parent has are expressed. For mammals, <1% of genes are imprinted.

Question 46

How goes imprinting work in relation to the germ line?

Answer 46

For both sperm and eggs, imprinting is reset and made to align with that of the parent regardless of the origin of the allele. So whether or not a gene gets expression depends on whether or not they inherited an expressed copy from the mother or the father.