Inheritance

Question 1

EXPLAIN meiosis

Answer 1

.meiosis halves the number of
chromosomes in gametes and fertilisation restores the full number of
chromosomes.
Cells in reproductive organs divide by meiosis to form gametes.
When a cell divides to form gametes:
* copies of the genetic information are made
* the cell divides twice to form four gametes, each with a single set of
chromosomes
* all gametes are genetically different from each other.
Gametes join at fertilisation to restore the normal number of
chromosomes. The new cell divides by mitosis. The number of cells
increases. As the embryo develops cells differentiate.

Question 2

define mitosis

Answer 2

a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth: Compare with meiosis

Question 3

Difference between meiosis and mitosis

Answer 3

meiosis leads to non-identical cells
being formed while mitosis leads to identical cells being formed

Question 4

what is the difference between sexual reproduction and asexual reproduction

Answer 4

In sexual reproduction there is mixing of genetic information which leads
to variety in the offspring. The formation of gametes involves meiosis.
Asexual reproduction involves only one parent and no fusion of gametes.
There is no mixing of genetic information. This leads to genetically
identical offspring (clones). Only mitosis is involved

Question 5

what is the difference between sexual reproduction and asexual reproduction

Answer 5

In sexual reproduction there is mixing of genetic information which leads
to variety in the offspring. The formation of gametes involves meiosis.
Asexual reproduction involves only one parent and no fusion of gametes.
There is no mixing of genetic information. This leads to genetically
identical offspring (clones). Only mitosis is involved

Question 6

Advantages of sexual reproduction

Answer 6

• produces variation in the offspring
• if the environment changes variation gives a survival advantage by natural
  selection
• natural selection can be speeded up by humans in selective breeding to
  increase food production

Question 7

Advantage of Asexual reproduction

Answer 7

• only one parent needed
• more time and energy efficient as do not need to find a mate
• faster than sexual reproduction
• many identical offspring can be produced when conditions are favourable

Question 8

Explain organisms reproducing sexually and asexually depending on the circumstances

Answer 8

• Malarial parasites reproduce asexually in the human host, but sexually in
  the mosquito.
• Many fungi reproduce asexually by spores but also reproduce sexually to
  give variation.
• Many plants produce seeds sexually, but also reproduce asexually by
  runners such as strawberry plants, or bulb division such as daffodils.

Question 9

What is DNA and describe it

Answer 9

The genetic material in the nucleus of a cell is composed of a chemical
called DNA. DNA is a polymer made up of two strands forming a double
helix. made from four
different nucleotides. Each nucleotide consists of a common sugar and
phosphate group with one of four different bases attached to the sugar.The DNA is contained in structures called chromosomes.

Question 10

what is a gene

Answer 10

A gene is a small section of DNA on a chromosome. Each gene codes
for a particular sequence of amino acids, to make a specific protein

Question 11

what is the genome

Answer 11

The genome of an organism is the entire genetic material of that organism.

Question 12

STOPPED AT PG 4 IN SPECIFICATION