Also for the first summative, second part

Question 1

Crossing over (words + diagrams)

Answer 1

Crossing over refers to the exchange of DNA between paired homologous chromosomes (one from each parent) that occurs during the development of egg and sperm cells (Prophase I, meiosis).

Question 2

Independent assortment (words + diagrams)

Answer 2

The law of independent assortment states that the random sorting of homologous chromosome pairs (or just chromosomes) during metaphase I (and 2?) allow for the production of gametes with many different assortments of chromosomes

Question 3

How DNA, genes, chromosomes, alleles account for the transmission of hereditary characteristics

Answer 3

Alleles:
- Alleles are the basic course of variation and diversity which is important for the formation of healthy organisms and stable, sustainable populations.

Genes:
- The different versions of the genes are known as alleles. One is inherited from the father, and one from the mother. Genes are sections of DNA that contain genetic information for the inheritance of specific traits.

DNA:
- The information coded in DNA is hereditary, meaning that it passes from parent to child. Because of this inheritance, DNA also determines our traits: including how we are shaped and how similar we look to our parents.

Chromosomes:
- The union of these two haploid cells at fertilization creates a new diploid organism, now containing one member of each chromosome pair derived from the male and one from the female parent. The behavior of chromosome pairs thus parallels that of genes, leading to the conclusion that genes are carried on chromosomes.

Question 4

Process of nondisjunction and how it results in the wrong number of chromosomes in a gamete

Answer 4

What is it?
- The failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division

How it results in the wrong number of chromosomes?
- If nondisjunction occurs during anaphase I of meiosis I, this means that at least one pair of homologous chromosomes did not separate. The end result is two cells that have an extra copy of one chromosome and two cells that are missing that chromosome.
- Nondisjunction in meiosis II results from the failure of the sister chromatids to separate during anaphase II. Since meiosis I proceeded without error, 2 of the 4 daughter cells will have a normal complement of 23 chromosomes.

P.S. remember diagrams!!!!! (this is a hint, Look at them)

Question 5

Meiosis VS. Mitosis–major differences & similarities

(Cover with fingers and go one by one–actually use paper.)

There are 11 in total points.

Answer 5

Cell type of parent cell:
- Both diploid

Number of daughter cells produced
- (Meiosis) 4
- (Mitosis) 2

Cell type of daughter cells:
- (Meiosis) Haploid
- (Mitosis) Diploid

Number of cell divisions:
- (Meiosis) 2
- (Mitosis) 1

Genetic relationship of daughter cells to parent:
- (Meiosis) NOT genetically identical
- (Mitosis) Genetically identical

Genetic relationship of daughter cells to one another:
- Same as answer straight above.

1. Synapsis occurs in (Prophase I) Meiosis BUT NOT in Mitosis
2. After stage I of Meiosis, the daughter cells are:
   - haploid.
3. Stage II of Meiosis is necessary to:
   - Separate double stranded chromosomes into single stranded chromosomes.
4. Stage II of Meiosis is most similar to Mitosis because:
   - Double stranded chromosomes (sister chromatids) are separated, rather than homologous pairs.
5. Every zygote is a:
   - Diploid cell because it comes from the fusion of 2 haploid cells.

Question 6

Examples of human genetic disorders that can result from a gamete with the wrong number of chromosomes combining with a gamete with the correct number of chromosomes

Answer 6

Down syndrome:
- Trisomy 21 (3 copies of chromosome 21)
- While chromosome 21 is the smallest human chromosome, it can still cause severe effects.

Klinefelter syndrome male:
- XXY

Trisomy X female:
- XXX

Jacob’s syndrome male:
- XYY

Turner syndrome female
- XO

Question 7

Trisomy and monosomy

Answer 7

Trisomy:
- cells in new individual have 3 copies of a chromosome

Monosomy:
- cells in new individual have only 1 copy of a chromosome.

Question 8

Aneuploidy

Answer 8

The occurrence of one or more extra or missing chromosomes in a cell or organism. Aneuploidy refers to any chromosome number that is not an exact multiple of the haploid number of chromosomes (which is 23 in humans).

Question 9

Homologous chromosomes and their genes.

Answer 9

Homologous chromosomes carry genes for the same traits such as hair colour, at the same location. However, they can carry different forms of the same gene. Different forms of the same gene are called alleles.