Chromosones, Genes And DNA

Question 1

Define heterochromatin

Answer 1

Genes are not expressed in this form and DMA is packaged onto solenoid fibres.

Question 2

Define Euchromatin

Answer 2

Genes are expressed in this form and DNA is on beads on a string form.

Question 3

What is a gene?

Answer 3

A length of DNA that carries a code for a protein.

Question 4

How are nucleotides joined?

Answer 4

Phosphodiester bonds in a 5’ to 3’ direction.

Question 5

Name the pyrmadines

Answer 5

Cytosine, Uracil, thymine

Question 6

Name the purines?

Answer 6

Guaine, adenine.

Question 7

How large is a turn of the DNA double helix?

Answer 7

3.4 nm

Question 8

How many hydrogen bonds between A and U?

Answer 8

2

Question 9

How many hydrogen bonds between g and c?

Answer 9

3

Question 10

What is the sequence of gene expression?

Answer 10

DNA ➡️ RNA ➡️ Protein

Question 11

Explain how DNA replicates in the human body?

Answer 11

Moving replication fork created by DNA helicase, which unwinds the double helix. DNA polymerase extends the 3’ ends only, leading to a continuous leading strand and a discontinuous lagging strand consisting of Ozaki fragments. Termination occurs when two replication forks meet, and the Ozaki fragments are joined by DNA ligase .

Question 12

What is the direction of DNA replication, and the enzyme that performs DNA replication?

Answer 12

5’ to 3’ direction, and the enzyme that performs it is DNA polymerase .

Question 13

What are the stages of mitosis?

Answer 13

Prophase, prometaphase, metaphase, anaphase, telophase.

Question 14

What are the stages of meiosis?

Answer 14

Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II and Telophase II.

Question 15

What are the consequences of meiosis?

Answer 15

4 daughter cells, as well as maintaining a constant chromosome number from generation to generation, and creation of genetic diversity through independent assortment and crossing over.

Question 16

What are the cells at each cell of spermatogenesis?

Answer 16

Spermatogium, primary spermatocyte, spermatids, and mature sperm.

Question 17

What are the products of oogenesis?

Answer 17

A mature ovum and 3 polar bodies

Question 18

Define heterozygous

Answer 18

Two alleles of a gene are different

Question 19

Define homozygous

Answer 19

When the two alleles of a gene are the same

Question 20

Define Hemizygous

Answer 20

Only one gene on the X chromosome

Question 21

What are some key features of an autosomal recessive pattern of inheritance?

Answer 21

Heterozygotes unaffected, males and females equally affected, 2 heterozygotes can only have affected offspring whereas two carriers have a 25% chance of affected offspring. Can appear to spring up out of nowhere.

Question 22

What are the key features of a autosomal dominant pattern of inheritance?

Answer 22

Males and females equally affected, rarely found in a homozygous state, cannot skip generation, every affected person will have affected parents.

Question 23

What are the key features of X linked recessive inheritance?

Answer 23

Hemizygous males and homozygous females, every heterozygous female has a 50% chance of affected children, more common in males, affected males cannot pass the gene to sons.

Question 24

What is co-dominance?

Answer 24

When neither gene is dominant over another

Question 25

What is complementation?

Answer 25

When more than one gene contributes to a single phenotype.

Question 26

What is linkage?

Answer 26

When two genes are found on the same chromosome.

Question 27

What factors affect recombination frequency?

Answer 27

Whether genes are on the same chromosome, and how close the genes are on the chromosome.

Question 28

What are some of the causes of variation?

Answer 28

Mutation, crossing over, independant assortment.