Genetics 1.9

Question 1

Genotype

Answer 1

the genetic makeup of an organism;

the combination of 2 alleles for a particular characteristic. (one from the mother and one from the father)

Question 2

Phenotype

Answer 2

observable characteristic/physical expression of the gene/genotype (e.g. blue eyes or brown eyes)

Question 3

Heterozygous

Answer 3

Having 2 different alleles for a characteristic (e.g. Tt)

Question 4

Homozygous

Answer 4

Having two identical alleles for a characteristic (e.g. TT or tt)

Question 5

Dominant Allele

Answer 5

An allele that is always expressed (in the phenotype) if present in the genotype of an organism (written as a capital letter - ex. B) BB or Bb

Question 6

Recessive Allele

Answer 6

An allele that is only expressed if the Dominant allele is absent in the Genotype (written as a lowercase letter - ex. b)

Question 7

Gene

Answer 7

A section of DNA that codes for a specific characteristic/protein

Question 8

Allele

Answer 8

An alternative form of a gene.

Alleles code for the same characteristic (e.g. eye colour) however they have a slightly different order of bases, so they code for a particular trait (e.g. brown hair or blonde hair).

Question 9

Trait

Answer 9

A characteristic that an organism can pass on to its offspring through its genes.

Question 10

Complementary base pairing

Answer 10

A pairs with T

C pairs with G

Question 11

Homologus Chromosomes/Homologus Pairs

Answer 11

Pair of chromosomes of the same size and shape and have the same genes at the same locus points (but may have different alleles).

To form the pair, we inherit one chromosome from our mother and one from our father during fertilisation.

For each characteristic, we have two alleles, one that has come from the maternal chromosome (mother) and one from the paternal chromosome (father)

Question 12

DNA

Answer 12

Deoxyribose Nucleic Acid - Double helix-shaped molecule that Carries the genetic information for an organism in the form of a base code

Question 13

Chromosomes

Answer 13

Structures in the nucleus, each comprised of one coiled-up molecule of DNA containing thousands of genes.

Humans have 46 chromosomes (23 pairs) in every body cell
22 pairs of autosomes, and a pair of sex chromosomes (XX female or XY male)
23 of these chromosomes have come from your mother and 23 have come from your father.

Question 14

Nucleotides

Answer 14

The building blocks of DNA. Consists of a deoxyribose sugar, phosphate, and base - joined by hydrogen bonds

Question 15

Mitosis

Answer 15

A process of cell division for growth, repair, and replacement of old cells. It only occurs in somatic cells (body cells) and results in two genetically identical daughter cells.

Question 16

Test Cross

Answer 16

A cross between an organism with an unknown genotype and an organism with a homozygous recessive genotype (bb) to determine if an individual is heterozygous or homozygous dominant (pure bred)

Question 17

Pure Bred

Answer 17

having a homozygous genotype for a given trait

Question 18

Mutation

Answer 18

Permanent change in the base sequence of DNA in an organism that may result in the formation of a new Allele

(Can be Neutral, Harmful or Beneficial)

Question 19

Inherited Mutation

Answer 19

A mutation that occurs in the gametes (sex cells) and CAN be passed on to offspring during fertilisation. Caused by permanent change in the base sequence of DNA/gene

Question 20

Non-inherited Mutation

Answer 20

Mutation that occurs in the Somatic cells (body cells) and CANNOT be passed on to offspring. Caused by environmental factors during the lifetime of the organism

Question 21

Punnett square

Answer 21

used to predict the probability or chance of what an offspring’s phenotype and genotype will be.

Will give the EXPECTED ratios. this may or may not match up to ACTUAL results due to the random nature of each fertilisation.

Each time new offspring is created through fertilisation it is a new event and the same probabilities apply regardless of the phenotype or genotype of previous offspring.

Question 22

Pedigree Chart

Answer 22

A method for studying the inheritance of genes in a family.

Pedigrees give the ACTUAL or observed phenotypes (rather than a prediction)

Question 23

Variation

Answer 23

Differences between members of the same species that can be caused by genetic factors (what genes you are born with) and environmental factors

Question 24

Inherited Variation

Answer 24

Variation that is inherited from parents and can be passed down to offspring during sexual reproduction

Question 25

Non-inherited Variation

Answer 25

Variation acquired during an organisms lifetime from environmental effects that affect its somatic cells. this means that it can’t be passed down to offspring

Question 26

Gamete

Answer 26

Haploid sex cell; an egg or sperm cell

Question 27

Zygote

Answer 27

Fertilized egg cell (diploid) - formed by the union of two gametes - an egg and a sperm (both haploid)