genetics. why do offspring look like their parents? parents pass half of their dna to their...
TRANSCRIPT
Genetics
Why do offspring look like their parents?
•Parents pass half of their DNA to their offspring
•Heredity (Inheritance) - The passing of traits from one generation to the next
•Inherited Traits – characteristics that are passed from parent to offspring– Examples: Eye color,
Hair type, Face shape, Blood type
Chromosomes and Genes
•Chromosome – A structure found in the nucleus of a cell that contains DNA
•You have 46 chromosomes in every cell! (23 from mom and 23 from dad)
•Gene – A segment of DNA on a chromosome
How many genes are on this chromosome?
9
One Gene
•Our genes determine our traits
•Genes always come in pairs
•One gene from the pair is called an allele.
We talk about genes in 2 different ways:• Genotype – the pair of genes
(the 2 allele letters)• Phenotype – the physical
expression of the genes (what it looks like)
RrGenotype Phenotype
Dominant and Recessive Genes
•Dominant Trait – will be expressed in the phenotype when at least one UPPERCASE letter is present in the genotype– Dominant Genotypes:
RR & Rr
•Recessive Trait – will only be expressed in the phenotype if two lowercase letters are present in the genotype– Recessive Genotype:
rr
• Environmental factors can affect our traits– Nutrients affect: height,
weight, health– Temperature affects: fur
thickness, color of leaves– Injuries cause: scars– Sun Exposure affects: skin
color, hair color