exam 1

gene

A segment of DNA that codes for a specific trait (e.g., hair color).

allele

A variant form of a gene; each person inherits two alleles (one from each parent).

genotype

The genetic makeup (the actual alleles) of an individual.

phenotype

The observable, physical expression of genes.

dominant allele

Masks the expression of a recessive allele; represented by uppercase letters (e.g., A).

recessive allele

Expressed only if no dominant allele is present; represented by lowercase letters (e.g., a).

homozygous

Having two identical alleles (e.g., AA or aa).

heterozygous

Having two different alleles (e.g., Aa).

diploid (2N) cells

Cells that have 23 pairs of chromosomes (46 total).

haploid (1N) cells

Cells (gametes) that have 23 total chromosomes.

Cystic Fibrosis

A recessive genetic disorder where a faulty chloride channel leads to thick, sticky mucus in the pancreas and lungs.

X-linked inheritance

Traits on the X chromosome; males express recessive traits on their single X chromosome.

color blindness

An X-linked recessive condition that affects vision.

hemophilia

An X-linked recessive condition that affects blood clotting.

codominant alleles

Two alleles that are both expressed equally in the phenotype (e.g., A and B alleles in ABO blood groups).

Type O blood

Genotype OO; results from having both alleles as O.

free-hanging earlobes

Dominant trait represented by allele E.

widow's peak

A distinct downward hairline in the center of the forehead, controlled by the dominant allele W.

long palmar muscle

A recessive trait represented by allele l; detectable by feeling three tendons in the wrist.

blue eyes

Occurs with a homozygous recessive genotype (pp) lacking pigment in the iris.

PTC tasting test

A test to determine taster status; tasting bitterness indicates at least one dominant T allele.

meter (m)

Basic metric unit for length.

liter (L)

Basic metric unit for volume.

gram (g)

Basic metric unit for mass.

kilo- (k)

Metric prefix meaning 1000.

centi- (c)

Metric prefix meaning 1/100.

milli- (m)

Metric prefix meaning 1/1000.

conversion of milligrams to grams

242 mg = 0.242 g when the decimal is moved three places to the left.

0 °C on the Celsius scale

Freezing point of water.

100 °C on the Celsius scale

Boiling point of water.

ratio

A comparison of two quantities (e.g., 1:4).

proportion

An equation that sets two ratios equal (A/B = C/D).

heart rate calculation

Beats per minute = 60 s ÷ time per beat (e.g., if time per beat is 0.6 seconds, then heart rate is 100 beats/min).

whats the genotype for X^H , Y

no genotype

whats the phenotype for X^H , Y

normal clotting, male

whats the phenotype for X^h , Y

Hemophilia, male

Bleeders disease X^H (dominate)

normal clotting

Bleeders disease X^h (recessive)

Abnormal

X^H X^H

normal clotting female

X^H X^h

normal clotting, female carrier

X^h X^h

Hemophilia, female