Lesson 8 ( Genes And Now They Are Inherited)

Question 1

What is a gene?

Answer 1

A region of DNA made up of nucleotides.it is the molecular unit of heredity. A gene has between 300 and 1 000 000 base pairs.

Question 2

What is a chromosome?

Answer 2

It is a molecule of multiple molecules of DNA. Chromosome 1 contains 240 000 000 base pairs.

Question 3

How many genes are there in the human genome?

Answer 3

There are approximately 24 000 genes in the human genome.

Question 4

How are DNA, RNA and proteins related to one another?

Answer 4

DNA is transcribed into RNA and RNA is translated into proteins.

Question 5

What is the initial structure of a replicated chromosome?

Answer 5

Two sister chromatids linked by a centromere. On one side there is the short arm and on the other the long arm. Telomere is the bottom part of the long arm.

Question 6

What is contained in a telomere?

Answer 6

A repetitive sequence of DNA that shortens with each cell division.

Question 7

What is the average of times a cell can be divided?

Answer 7

I cell is divided 25 to 50 times until apoptosis.

Question 8

What is apoptosis?

Answer 8

It is programmed cell death to prevent copy errors or mutations inside cells.

Question 9

What is the ploidy of a cell?

Answer 9

It refers to the number of copies (sets) of each chromosomes.

Question 10

What is n?

Answer 10

N is the number of haploid chromosomes or the number of different chromosomes (unduplicated) in a species.

Question 11

What are somatic cells?

Answer 11

They represent all body cells except for gametes.

Question 12

What are somatic cells?

Answer 12

They represent all body cells except for gametes.

Question 13

What is N?

Answer 13

N is the number of duplicated chromosomes inside a cell.

Question 14

What is the karyotype?

Answer 14

The entire collection of chromosomes found in a cell or in an organism. In a karyotype, chromosomes are arranged by size (from largest to smallest) and numbered.

Question 15

What means aneuploidy?

Answer 15

It refers to an atypical number of chromosomes and there are two ways of causing it: non-disjunction on mis-division of chromosomes.

Question 16

In what phase of meiosis is a mistake made during non-disjunction of chromosomes?

Answer 16

During meiosis I when both chromosomes of the same pair are delivered to the same part of the spindle which produces two gametes with an extra chromosome (trisomy) and two gametes with a missing chromosome (monosomy).

Question 17

In what phase of meiosis is a mistake made in cells in the case of misdivision of chromosomes?

Answer 17

During meiosis Il, two atypical gametes are produced, a gamete with an extra chromosome (trisomy) and one gamete with a missing chromosome ( monosomy).