Lab 9 Flashcards
What is heredity?
Passing of genetic information from one generation to the next
Define chromosome.
One long threadlike molecule of DNA coiled together with several proteins
What do chromosomes contain?
Inherited genetic material - thousands of genes arranged along each chromosome in a certain order
What are homologous chromosomes?
Pairs of chromosomes that contain similar genes
What is the diploid number of chromosomes in humans?
46 chromosomes, 23 pairs of homologous chromosomes
What is the haploid number of chromosomes?
23 single chromosomes
What are gametes?
Ova / sperm cell
What are somatic cells?
Human body cells
What is a zygote?
Ovum + sperm, 46 chromosomes, 23 inherited from each parent
Define gene.
Biological unit of heredity
What are alleles?
Genes that code for the same trait and occupy the same location on homologous chromosomes
What is a homozygous allele?
Alleles that are identical and code the same way
What are heterozygous alleles?
Alleles that are different
What does genotype refer to?
Genetic makeup, combination of alleles present in chromosomes
Define phenotype.
The observable expression of the genotype
What are autosomes?
Chromosomes 1 to 22 that contain genes for most body characteristics
What are sex chromosomes?
The 23rd pair of chromosomes that determines the sex of an individual
Describe the Y chromosome.
⅓ the size of the X chromosome, lacks many genes found on the X chromosome
What is a karyotype?
Picture of the chromosomal makeup of an individual
What do Punnett squares show?
Possible combinations of inherited alleles in offspring for a trait controlled by a single pair of alleles
List the types of simple inheritance.
- Dominant-recessive
- Incomplete dominance
- Codominance
- Multiple-allele
- Sex-linked
What is dominant-recessive inheritance?
Dominant allele is expressed, recessive is suppressed
Define incomplete dominance inheritance.
Heterozygous alleles produce intermediate phenotype; a dominant allele does not completely mask effects of a recessive allele
What characterizes codominance inheritance?
Both alleles are dominant and equally expressed
What is multiple-allele inheritance?
More than 2 types of alleles code for a single trait
Define sex-linked inheritance.
Genes on the sex chromosomes where the dominant allele is completely expressed
What are chromosomal abnormalities?
Damaged, missing, or extra copies of chromosomes
What is Trisomy 21?
Extra copy of chromosome 21, known as Down syndrome
What affects the colour in the iris?
- Iris stroma
- Pigment epithelium
- Collagen and cell density in the stroma
Define polygenic trait.
Controlled by more than one gene
Can a blue-eyed parent have a brown-eyed child?
Yes, if the blue eyes are due to defects in HERC2 and OCA2 in the parents
What is the probability of boys inheriting an X-linked recessive disorder from a carrier mother?
50% chance
Will daughters inherit an X-linked recessive disorder from a carrier mother?
None will have it, but half are likely to be carriers
