Download Gene: Usually, a section of DNA long enough to code for a protein

VOCABULARY FOR GENETICS Gene: Usually, a section of DNA long enough to code for a protein molecule.
Some genes, however, instead control other genes.
DNA: A long linear molecule made up of four smaller molecules known as bases
(A, T, G, C). The order of bases is a code which specifies the order of amino acids
in a protein.
Amino acids: Small molecules made up of a dozen or two atoms. There are 23
different kinds of amino acids. A couple hundred or so amino acid molecules
strung together like beads on a string form a protein molecule.
Protein: A large molecule made up of a chain of amino acids. Proteins differ in
length and sequence of amino acids. Depending on the sequence, protein molecules
fold to take on a specific shape.
Enzyme: A protein which acts as a catalyst. Enzymes work by providing a place
where another molecule (or molecules) can fit and undergo a chemical change (ie
the substrate(s) might be split apart, joined, gain or lose atoms).
Substrate: The molecule(s) acted on by an enzyme. For example, your saliva
contains amylase, an enzyme which converts starch to sugar. Starch is the
substrate.
Active site: The site on an enzyme where the substrate(s) fits.
Catalyst: A substance that makes a chemical reaction happen faster but isn’t
consumed in the reaction. Enzymes are catalysts.
Metabolic pathway: A series of chemical reactions in a living cell in which a
substance is sequentially altered until a desired product is produced. Each step in
the pathway is assisted by a specific enzyme.
Chromosome: A tightly coiled piece of DNA long enough to include up to about
1000 genes.
Recessive gene: An inactive gene.
Alleles: Paired genes. Example: you inherited a gene for eye color from each of
your parents. Those two genes are alleles. They may not be identical; for example
one allele may code for brown eyes, the other for blue. Because blue is recessive,
your phenotype would be brown.
Phenotype: Describes the effect of a gene. White fur is a phenotype.
Genotype: Describes the genes an organism has inherited. In class a genotype
might be written as BB.
Homozygous: The organism has inherited the same allele from each parent. aa
Heterozygous: The organism has inherited different alleles for a given trait: Aa
Genome: The total genetic message or code in each sex cell. Each human sex cell
contains a genome of 3 billion base pairs making up 20,000 genes organized into
23 chromosomes.
Base pair: A DNA molecule is made up of a linear sequence of the bases A, T, G,
C Each T is paired with an A; each G is paired with a C to form pairs.
Mitosis: Normal cell division in which a (human!) cell with 46 chromosomes
divides to form two cells, each with 46 chromosomes.
Meiosis: Cell division in which a (human!) cell with 46 chromosomes divides to
form egg or sperm cells with 23 chromosomes each.
Sex chromosome: X or Ychromosomes which carry genes involved in gender
determination.
Autosome: Any of the non-sex chromosomes.
Linked genes: Genes are said to be linked if they are found on the same
chromosome.
ANSWERS TO GENETICS PRACTICE 1) Use a 1 x 2 Punnett square.
a) The man’s genotype is Bb
b) ½ of the children will be Bb; ½ will be bb.
2)
a) If the dog is DD, use a 1 x 1 Punnett square. All the offspring will be Dd
b) If the dog is Dd, use a 1 x 2 Punnett square. ½ of the pups will be hearing;
½ will be deaf.
c) Two heterozygous (Dd) dogs could have a deaf pup.
3)
a) Use a 1 x 1 Punnett square. All F1 ofspring will be pink.
b) Use a 2 x 2 Punnett square. ¼ of the F2 generation will be red, ½ pink,
and ¼ white.
4)
a) The parents are both heterozygous (Bb).
b) The F1 phenotype ration is 3 brown : 1 black.
5) Use a 2 x 2 Punnett square.
a) Parents genotypes: Ss
b) Normal appearing child has 2/3 chance of being a carrier.
c) Each successive child has a ¼ chance of having the disease.
6) Parent genotypes: RRtt x RrTt. Use a 1 x 4 Punnett square.
a) You expect 1/4 , or 3 children to be RRtt.
b) Use a 2 x 4 Punnett square.
7)
a) TtRr x ttRr
b) TTRr x ttRr
c) TtRR x ttRR
d) Ttrr x ttRr
8) Just figure out the phenotype ratio! Use a 4 x 4 Punnett square. You will find a
9 black : 3 gray : 4 albino ratio.