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Flashcards in B12 Deck (14):
1

Describe Asexual reproduction

-Done by mitosis
-No fusion of gametes
-No mixing of genetic information
-Leads to genetically identical offspring
-Only 1 parent

2

Describe sexual reproduction

-Fusion of male and female gametes
-Gametes are formed by meiosis which leads to the formation of non-identical cells (sperm and egg cells in mammals / Pollen and egg cells in plants)
-Mixing of genetical information that leads to variation in the offspring

3

What is a genome ?

The entire genetic material of an organism

4

Why is studying the human genome important ?

-Search for genes linked to different types of disease
-Genetic modification to benefit future generations
-understanding treatment of inherited disorders
-tracing human migration patterns from the past

5

What is DNA ?

-The composition of genetic material in the nucleus
-A polymer made up of two strands forming a double helix

6

What is a gene ?

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

7

What do the following terms mean:
Homozygote
Heterozygote
Genotype
Phenotype

Homozygote: An individual with two identical alleles for a characteristic
Heterozygote: An individual with different alleles for a characteristic
Genotype: Describes the alleles present or genetic makeup of an individual regarding a particular characteristic
Phenotype: The physical appearance of an individual regarding a particular characteristic e.g. black or brown fur in a mouse

8

What is a dominant and recessive allele ?

Dominant: Only one of these allele must be present to control the characteristic, often represented with a capital letter
Recessive: Both alleles must be present in order to control the characteristic, often represent with a lower case equivalent of the letter

9

Name 2 genetic diseases and how they are inherited

Polydactyly, development of extra body part e.g. finger:
-Caused by a dominant allele which can be inherited from both parents
Cystic Fibrosis, prevents movement of certain substances in the body leading to a build up of thick mucus:
-inherited via a recessive allele

10

How can genetical diseases be discovered before a baby is born ?

Genetic Screening:
-Amniocentesis carried out at 15-16 weeks of pregnancy, involves taking fluid around foetus and developing foetus. This fluid contains. Fetal cells which can be used for screening
-Chronic villus sampling done between 10-12 weeks of pregnancy by takin a sample of tissue from the developing placenta which provides fetal cells to screen

11

What are some disorders that come about by inheritance ?

Polydactyly:
-caused by a dominant allele and it causes extra fingers or toes
Cystic Fibrosis:
-Caused by a recessive allele, it is a disorder of cell membranes

12

How does sexual reproduction work in animals and plants ?

Animals:
-fusion of sperm and egg cells
Plants:
-Pollen and egg cells fuse

13

What is meiosis and how does it work ?

Meiosis is the division of cells to form gametes:
-Copies of genetic information are made
-Cells divide twice to form four gametes, each with one set of chromosomes (23 in humans)
-All gametes are genetically different

14

Define the following terms:
-Gamete
-Chromosome
-Allele

Gamete:
-cell that unites with another of the opposite sex to form a zygote
Chromosome:
-A thread-like structure of nucleic acids and protein carrying genetic information in the form of genes
Allele:
-Different forms of the same Gene, either dominant or recessive, that controls the outcome of a characteristic