Genes and Traits

Question 1

Hierarchy of DNA

Answer 1

DNA ↣ Chromosomes ↣ Genes ↣ Traits

→ Humans have 46 chromosomes (23 pairs of chromosomes)
↪ One complete set of 23 chromosome from father and one set of 23 chromosome from your mother

Question 2

Genetics

Answer 2

The study of heredity and variation in an organism; how traits are passed on from generation to generation

Question 3

Genes

Answer 3

Genetic material on a chromosome that codes for a trait.

Question 4

Trait

Answer 4

A distinguishing characteristic of an individual (Can be inherited)

Question 5

Inherited Trait

Answer 5

A characteristic transmitted from one generation to the next

Question 6

Alleles

Answer 6

Variations of genes
→ You can contain two copies of each gene that are not identical (one from father and one from mother)

Example if fur colour was a gene, Orange fur colour and blue fur colour would be alleles.

Question 7

Dominant Allele

Answer 7

A dominant allele is a trait that will be expressed regardless of the second allele.

Question 8

Recessive Allele

Answer 8

A recessive allele is a trait that will be shown only if both parts of the allele are recessive. Dominant will always mask recessive traits.

Question 9

Genotype

Answer 9

Specific alleles that make up a trait (Usually letters)

Question 10

Phenotype

Answer 10

How the trait is expressed. If eye colour was the gene, Phenotypes would be blue or brown.

Question 11

Homozygous Genotypes

Answer 11

These are Genotypes that have two of the same allele for a trait
→ Can be homozygous dominant if both alleles are dominant
→ Can be homozygous recessive if both alleles are recessive

Question 12

Heterozygous

Answer 12

Having two different alleles for a trait

Question 13

Incomplete dominance

Answer 13

A condition where neither of the two alleles for the same gene can completely mask each other.
↪ So the heterozygous offspring will demonstrate a phenotype that is a mix of the recessive and dominant traits
↪ Superscripts need to be used for incomplete dominance as there is no recessive or dominant trait (They are kinda equal)

Question 14

Codominance

Answer 14

When both alleles are fully expressed.

For example a cow at codominant genes defining fur colour, thus the white and black fur colouration.

→ Superscripts are used for codominance as both genes are expressed so there is no dominant or recessive

Question 15

Polygenic Traits

Answer 15

Traits that need more than one gene to be expressed (most traits are polygenic).

Question 16

Pleiotropic Genes

Answer 16

Genes that affect how many other genes will be expressed.

Question 17

A Note on Mendel

Answer 17

In 1853 an Austrian Monk set out to explain heredity and took 8 years to complete his studies using pea plants.

He used pea plants as they have a short reproductive cycle, are easy to grow, distinguishable characteristics such as short vs long stems, wrinkled vs smooth, self pollinate (both pistil and stamen in same flower) so cross-pollination was easy to perform and keep track of, easily accessible in Europe in the time period.

Question 18

Purebred | Truebred

Answer 18

Purebred is just organisms with homozygous traits. In Mendel’s experiments these were used as the parent generation.

Question 19

Carrier | Hybrid

Answer 19

Heterozygous traits. In Mendel’s experiments the F1 generation were hybrids.

Question 20

Mendel Disapproved

Answer 20

Theory of blended Inheritance

Question 21

Multiple Allelism

Answer 21

When there are more than two possible alleles for a given gene (e.g. eye color, ABO blood types), results in a larger number of possible genotypic combinations and a greater variety of phenotypes.

Question 22

Inbreeding is discouraged because

Answer 22

It increases chances the risks of recessive gene disorders. Since people are in the same blood pool there is a high chance that two inbred partners will both carry the recessive gene.