lab 5: human karyotype analysis and genetics

How many chromosomes do humans have?

46 (23 pairs) and 2 sex chromosomes

Karyotype

A display of the chromosome pairs of a cell arranged by size and shape.

metacentric

centromere in middle

subterminal

centromere is located between the middle and the end of the chromosome

acrocentric

centromere close to end

Nondisjunction

Error in meiosis in which homologous chromosomes fail to separate.

Trisomy 21

condition in which an individual has three number 21 chromosomes, resulting in Down syndrome

Trisomy 13

Extra 13th chromosome - patau syndrome

Severe birth defects: clefts, extra fingers/toes

Often heart, brain or spinal abnormalities

Short life span

trisomy 18

Edwards syndrome

XXY syndrome

Klinefelter's syndrome

Cr du Chat

loss of about half of the short arm of one member of the homologous pair for chromosome 5

Turner's syndrome

Born with a single X chromosome. (short, webbed neck, different physical sexual development.)

Phenylketonuria (PKU)

an inherited disorder of protein metabolism in which the absence of an enzyme (liver enzyme) leads to a toxic buildup of certain compounds, causing intellectual disability

locus

Location of a gene on a chromosome

Genotype

genetic makeup of an organism

Phenotype

An organism's physical appearance, or visible traits.

Allele

Different forms of a gene

dominant allele

An allele whose trait always shows up in the organism when the allele is present.

ressesive allele

An allele that is hidden whenever the dominant allele is present

Homozygous

An organism that has two identical alleles for a trait

Heterozygous

An organism that has two different alleles for a trait

first filial generation

The first generation of offspring resulting from a cross of two parent organisms, abbreviated the F1 generation.

second filial generation

The offspring resulting from a cross between members of the first filial (F1) generation

monohybrid cross

A cross between individuals that involves one pair of contrasting traits

dihybrid cross

Cross or mating between organisms involving two pairs of contrasting traits

incomplete dominance

A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. The resulting offspring have a phenotype that is a blending of the parental traits.

multiple allele inheritance

occurs when there are more than two different alleles of a gene for a particular trait

polygenic inheritance

combined effect of two or more genes on a single character

sex-linked traits

Traits controlled by genes located on sex chromosomes.

how to answer a genetic problem

1. define alleles 2. determine genotypes of parents and the gametes that can be produced (using punnet square) 3. express results