Q2L2 BIO_Genetics and Inheritance

Genetics

Study of genes and their transmission from one generation to the next

Genes

a discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA. it contain instructions for building proteins

Genome

it is the complete genetic material of an organism along with its noncodinf nucleic acid sequence

structures within the nucleus, composed of DNA and protein

• the genes are located on the chromosomes

• Humans: 46 chromosome, 23 pairs

Chromosomes

First 22 pairs

How many pairs are the body chromosomes (autosomes)

Last 1 pair

What is the sex chromosome (allosome)

Karyotype

a composite visual display of all the chromosomes of an individual. shows all 23 pairs of chromosomes lined up side-by-side

each pair of autosome carries the same genes at the locus

What do the pair of autosomes carry?

Gene locus (plural: loci)

location of the specific pair of genes

Yes, normally, a pair of genes have the same structure and function

Yes or no, do both genes have the same structure and function

Alleles

alternative versions of the same gene pair

Types of Alleles

• Homozygous

• Heterozygous

• Hemizygous

Homozygous

two identical alleles at a particular locus

Heterozygous

two different alleles at a particular locus

• hybrid

• dominant & recessive

Hemizygous

only one allele is present (ex. XY)

Homologous Chromosomes

• one member of each pair is inherited from each parent

• look alike (size, shape, banding pattern)

• Not identical: may have different alleles of particular gene

Dominant allele

• masks or suppresses the expression of its complementary allele

• always expressed even if heterozygous

• Genotype: AA, Aa

No, they are not necessarily more common; sometimes they may be rare in a population

Are dominant alleles more common than recessive ones?

Recessive allele

• will not be expressed if paired with a dominant allele (heterozygous)

• will only be expressed if individual is homozygous for the recessive allele

• Genotype: aa

Genotype

an individual’s complete set of alleles 

• codes/ basis for the phenotype

• used in punnet squares

• Ex. AA, Aa, aa

Phenotype

observable physical and functional traits

• Ex. Hair color, eye color, skin color, blood type

• determined by inherited alleles and environmental factors

Gregor Mendel

• Father of modern genetics

• worked with pea plants in the 1850s in Austria

• did multiple genetic experiments to develop basic rules of inheritance

1. law of segregation

2. law of independent assortment

3. law of dominance

What are the laws of inheritance developed by Gregor Mendel?

Law of dominance

according to the law of dominance, hybrid offspring will only inherit the dominant trait in the phenotype

• in a heterozygous allele, the dominant trait will be reflected in the offspring

Law of segregation

The law of segregation states that during the production of gametes, two copies of each hereditary factor segregate so that offspring acquire from each parent

• separated to prepare for fertilization

Law of independent assortment

The law of independent assortment states that a pair of traits segregates independently of another pair during gamete formation. As the individual heredity factors assort independently, different traits get equal opportunity to occur together.

• best seen in a dihybrid testing