L1 Genetics - biology

Question 1

DNA

Answer 1

• DNA stands for deoxyribonucleic acid
• DNA is in a form of a double helix/twisted ladder
• DNA is a self-replicating material that is present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information.
• DNA is made up of nucleotides

Question 2

Nucleotides

Answer 2

Nucleotides form the basic structural unit of DNA. Composed of sugar, a phosphate and a nitrogen base.
Four nitrogen bases:
Adenine (A) pairs with Thymine (T)
Guanine (G) pairs with Cytosine (C)

Question 3

Allele

Answer 3

Different forms of the same gene. They can be either dominant or recessive.
- Allele determines phenotype

Question 4

Phenotype

Answer 4

The observable characteristics of an individual resulting from its genotype.

Question 5

Chromosome

Answer 5

Threadlike structure of DNA that contains genes and is found in the nucleus of a cell. It is made up of proteins and DNA organized into genes. Each cell contains 23 pairs of chromosomes.

Question 6

Gene

Answer 6

A segment of DNA, coding for a protein that determines the trait/characteristic of an individual.
- Gene determines genotype

Question 7

Genotype

Answer 7

The two alleles available in the individual

- Homozygous OR heterozygous

Question 8

Protein

Answer 8

Protein are large, biologically important polymers comprised of sequences of amino acids

Question 9

Trait

Answer 9

A genetically determined characteristic or condition. Traits can be determined by genes or the environment.
e.g fin length, body shape, eyesight, etc

Question 10

Advantages and disadvantages of sexual reproduction

Answer 10

Advantages
- There is a variation as the offspring will carry the alleles from both parents mixed together.
- Offspring will most likely be more protected
Disadvantages
- Time-consuming as you need to find a partner
- Takes longer than asexual reproduction

Question 11

Amino acid

Answer 11

Amino acids are small molecules that are the building blocks of proteins.

Question 12

Difference between sexual and asexual reproduction

Answer 12

Sexual Reproduction
- Involves two parents and produces offspring that are genetically unique.
Asexual reproduction
- Only involves one parent and produces offspring that are genetically identical to each other and to the parent.

Question 13

Advantages and disadvantages of asexual reproduction

Answer 13

Advantages
- Organisms do not need to find partners, therefore is less time-consuming.
Disadvantages
- No variation which means any negative mutation or changes will be passed on to offspring.
Short lifespan

Question 14

Variation

Answer 14

The difference between individuals which is genetically inherited

Question 15

Genetic variation

Answer 15

Mutagens cause genetic variation

Question 16

Diploid

Answer 16

Diploid are two copies of every chromosome

Question 17

Environmental factors

Answer 17

Any factor that influences es living organisms.

- Sound, light, parasites, temperature

Question 18

Zygote

Answer 18

The name of the first cell created by fertilisation

Question 19

Gametes

Answer 19

Specific names for sex cells 
Female gamete
- Egg
Male gamete
- Sperm

Question 20

Haploid

Answer 20

Haploid are cells that have a single set of chromosomes

Question 21

Mitosis

Answer 21

Type of division used to produce

Question 22

Meiosis

Answer 22

Type of division used to produce cells (gametes)

Question 23

Homozygous

Answer 23

pairs of chromosomes that code for the same characterisitic

Question 24

Heterozygous

Answer 24

Having two different alleles of a particular gene/genes

Question 25

Recessive

Answer 25

The allele is always expressed when no dominant allele is present (homozygous recessive)
- Expressed through lower case letters (a,b,c)

Question 26

Dominant

Answer 26

The allele is always expressed when present

- Expressed through capital letters (A, B, C)

Question 27

Mutation

Answer 27

A mutation is a change that occurs in our DNA sequence, either due to mistakes when the DNA is copied or as the result of environmental factors such as UV light and cigarette smoke.

Question 28

Causes of mutation

Answer 28

• DNA copying mistakes during cell division
• Exposure to radiation (e.g x-rays)
• Exposure to chemicals (mutagens)
• Infection to viruses

Question 29

Examples of mutation

Answer 29

• Cystic fibrosis
• Down syndrome
• ## Sickle-cell anemia

Question 30

Types of mutation

Answer 30

Gene mutation

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