BIOLOGY! – GENETICS!

What is DNA? What makes up DNA? DNA stands for deoxyribonucleic acid and contains genetic information. It is found on chromosomes located in the nucleus of our cells. DNA Image: http://science.howstuffworks.com/genetic-science/dna-evidence.htm What makes up DNA? The sides or backbone of the DNA molecule are made up of sugar (deoxyribose) and phosphate molecules. The rungs that form the middle of the molecule are made up of pairs of nucleotides or nitrogen bases. Adenine (A) pairs with thymine (T), while guanine (G) always pairs with cytosine (C). The order of the bases determines the genetic code. Double Helix

One reason people study genetics is to predict the likelihood that someone will inherit a particular traits.   This probability is used by breeders to develop plants, pets, and livestock but it has also been used to trace genetic traits in families.

In humans, we have 23 pairs of chromosomes (46 total) in every cell. HALF from each biological parent.

GENES - a distinct sequence of bases (AGTC) which form part of a chromosome - the order determines what amino acids (and therefore proteins) a cell will make Gene

Gene ALLELES - the type or variation of the gene, any of several forms of a gene Ex. Gene = hair colour Alleles = brown hair, blond hair, black hair, red hair, etc.

Phenotype: Genotype:

Genotype describes the genetic make-up of an organism (the combination of alleles), Phenotype describes the observable characteristics that the organism has. (How it physically exhibits the alleles that it’s coded for)

For each type of gene, we get one allele from our biological mother and one allele from our biological father from their chromosomes.

DOMINANT ALLELES produce the same phenotype whether its paired allele is identical or different (this trait is always expressed/seen) RECESSIVE ALLELES produce its characteristic phenotype only when its paired allele is identical (this trait isn’t as commonly expressed/seen)

Dominant and Recessive Body Size H (Dominant Allele) h (Recessive Allele)

Dominant and Recessive Body Size Offspring: Genotype is Hh Phenotype is large body (H)

Heterozygous H h Heterozygous – one dominant and one recessive allele (the alleles are different)

Homozygous Dominant H H Homozygous – two of the same alleles

Homozygous recessive h h

Punnett Squares Bob’s mum: Bb (She is ________________________________) Bob’s dad: BB (He is ______________________ ) B= Brown eyes b= blue eyes What are the possible genotypes of Bob? What are the possible phenotypes of Bob?