Dental Genetics 1: Introduction to Inheritance, Genes & Alleles

Genotype

Genetic makeup of an organism

Phenotype

Observable traits of an individual

How many alleles in a gene? How are they inherited?

Two, one inherited from each parent

Homozygous

Alleles are the same.

Heterozygous

Alleles are different

How many chromosomes and pairs in a human body?

46, 23 pairs

What does a homozygous-dominant allele display?

Dominant trait.

What does a heterozygous allele display?

Dominant trait

What does a homozygous-recessive allele display?

Recessive trait.

Male and Female Sex Chromosomes

Males are XY, Females are XX.

Heredity and Variation

Genes are passed on from parents to the next generation, but we are not exact copies of our parents. There is some variation.

What do chromosomes hold?

Chromosomes hold DNA, which has the genes required to determine an individual’s traits

The role of genes in simple and complex dental traits.

Genes can affect simple dental traits like having a Carabelli’s trait/cusp. It can also determine the amount of saliva someone produces or their enamel resistance

Mendel's laws

Law of Dominance and Uniformity, Law of Segregation, Law of Independent Assortment

Law of Dominance and Uniformity

In heterozygous alleles, the dominant trait will be shown while the recessive trait is masked.

Law of Segregation

Each individual has two alleles for each trait, but during gamete formation, these alleles separate, so each gamete only carries one allele.

Law of Independent Assortment

Different traits are inherited independently of each other, meaning the allele for one trait cannot influence the allele for another trait during gamete formation.

Primary Structure of DNA

Has nucleotides made up of a phosphate group, deoxyribose sugar, and four nitrogenous bases. Nucleotides are linked by phosphodiester bonds, forming a sugar-phosphate backbone. Nitrogenous bases along the DNA strand carries the genetic information. 

Secondary DNA Structure

Two long, complementary strands of nucleotides twist around each other to form a double helix. The two strands are held together by hydrogen bonds between the base pairings.

Tertiary DNA Structure

DNA has proteins called histones. It wraps around these histones, forming nucleosome structures. Nucleosomes are organised into structures called chromatin, which is a complex of DNA and proteins.

Understand the concept of redundancy in the genetic code.

Nucleotides code for amino acids. Redundancy in genetic code means that multiple codons (three nitrogenous base sequences) can make the same amino acid, so mutations to the base doesn’t change the amino acid.

What does the square represent in a pedigree?

Male

What does the circle represent in a pedigree?

Female

What does the coloured in squares/circles represent in a pedigree?

The male/female has the characteristic

What does it mean if the squares/circles are not coloured in a pedigree?

The male/female does not have the characteristic.

What does a double line show in a pedigree?

Imbreeding, where two parents of affected individuals could be genetically related.