class

Question 1

homologous Chromosomes

Answer 1

pair of chromosomes in diploid organisms that have the same structure as each other, with the same genes (but not necessarily the same alleles) that form a bivalent during the first division of meiosis. they have the same length, staining position, and centromere position.

Question 2

gene

Answer 2

section of DNA/ sequence of nucleotides that code for a particular polypeptide.

Question 3

allele

Answer 3

it is a particular variety of a gene, that is, one or more alternative nucleotide sequence at a specific gene locus

Question 4

locus

Answer 4

the position at which a particular gene is found on a particular chromosome. the same gene is always found on the same chromosome.

Question 5

diploid

Answer 5

a cell that possesses 2 complete sets of chromosomes

Question 6

haploid

Answer 6

a cell that possesses one complete set of chromosomes

Question 7

Meiosis

Answer 7

reduction division, a nuclear division that halves the chromosome number or else number of chromosomes would double every generation.

Question 8

Outline the process of Meiosis 1

Answer 8

Reduction division to form half the number of chromosomes
bivalents form, where homologous chromosomes pair up
crossing over at the chiasmata
independent assortment
spindles attach to kinetochores at centromeres
chromosomes of each pair pulled to opposite poles by shortening of spindle fibres
nuclear envelope begins to reform
cytokinesis occurs

Question 9

independent assortment

Answer 9

each homologous pair of chromosomes are arranged randomly so each pair can orient freely towards either pole, pairs, therefore, become pulled to different poles independently

Question 10

crossing over

Answer 10

produces recombinant chromosomes, individual chromosomes contain genes from different parent genes.

Question 11

random fertilization

Answer 11

the fusion of the male and female gametes, where the mating is random

Question 12

Spermatogenesis

Answer 12

germinal epithelial cells undergo cell division repeatedly, that become spermatogonia. diploid spermatogonia increase in size and become diploid primary spermatocytes. Primary spermatocytes undergo meiosis 1, to form haploid secondary spermatocytes. Secondary spermatocytes undergo meiosis 2 to form spermatids, they are provided with nutrients by the Sertoli Cells that surround the testis and also protects them from attack from the immune system. Spermatids mature into sperm.

Question 13

Oogenesis

Answer 13

germinal epithelial cells form oogonia
Oogonia increase by mitosis
Oogonia are still diploid
Oogonia then begin Meiosis and form primary oocytes
meiosis stops at prophase 1
the above occurs in the embryo
Primary oocytes complete Meiosis starting from puberty and produce secondary oocytes and the first polar body
there are 2 haploid cells with 2 DNA units
secondary oocytes are released as an ovum, and undergo meiosis at fertilization, and forms a second polar body.

Question 14

Gametogenesis in plants

Answer 14

In the Anther:
diploid pollen mother cells divide by meiosis to form 4 haploid cells. The nuclei of each haploid then divide by mitosis, but the cell itself does not undergo cytokinesis, each contains 2 haploid nuclei. As they mature into a pollen grain, the two nuclei become the tube nuclei and the generative nuclei.
In the Stamen:
inside each ovule, a large, diploid mother cell develops. This cell divides by meiosis to form 4 haploid cells. 1 surviving haploid cell become the embryo sac. the grows larger and undergoes meiosis 3 times to form 8 haploid nuclei. One of these becomes the female gamete.

Question 15

homozygous

Answer 15

having 2 identical alleles of a gene

Question 16

heterozygous

Answer 16

having 2 different alleles of a gene

Question 17

Dominant Allele

Answer 17

an allele that always expresses itself in the phenotype even in the presence of an alternative allele.

Question 18

Recessive Allele

Answer 18

an allele that is only fully expressed when no dominant allele is present

Question 19

Codominance

Answer 19

both alleles have an effect on the phenotype of a heterozygous organism

Question 20

F1

Answer 20

offspring resulting from a cross between an individual between a homozygous dominant with a homozygous recessive genotype

Question 21

F2

Answer 21

Offspring resulting from a cross between two F1 organisms

Question 22

Test cross

Answer 22

genetic cross in which an organism showing a characteristic caused by a dominant allele is crossed with an organism that are homozygous recessive; the phenotypic of the offspring can be a guide to whether the first organism was homozygous or heterozygous

Question 23

sex linkage

Answer 23

where an allele linking to a disease is found on the X chromosome. females have 2 copies of the gene, males have one

Question 24

Autosomal linkage

Answer 24

the linkage is the presence of two genes on the same chromosomes with very close loci, so that they tend to be inherited together and do not assort independently

Question 25

mutation

Answer 25

causes genetic variation. It is a random/spontaneous change in the DNA base sequence, caused by mutagens such as ionizing radiation. They involve things like Base substitution or base addition or deletion. Usually resulting in the synthesis of a different polypeptide

Question 26

Frameshifts

Answer 26

usually occurs when there are base substitutions or deletion, the changed area causes a change in the DNA base sequence along the entire chain. A Non-sense occurs when it creates a premature stop triplet

Question 27

Silent mutation

Answer 27

common in base substitutions, where the change in the base sequence has no effect on the synthesized polypeptides in any way.

Question 28

Albinism

Answer 28

the relationship between a gene, an enzyme and a human phenotype. Tyrosine => DOPA => dopaquinone => Melanin (dark pigment). The homozygous recessive allele causes an inactive or absence of Tyrosinase enzyme, that converts DOPA into dopaquinone, resulting in a lack of melanin production.

Question 29

Huntington’s

Answer 29

a dominant allele, causing a neurological disorder, unstable segment in a gene on chromosome 4 coding for a protein, huntingtin. They have a large number of repeats called stutters.