LAB 9- Heredity Flashcards
Heredity
passing of genetic
information from one
generation to the next
Types of inheritance
‒ Complete dominance
‒ Incomplete dominance
‒ Co-dominance
‒ Sex-linked inheritance
-Multiple-Allele Inheritance
Chromosome
long thread molecule of
DNA coiled with proteins
‒ Contains the inherited genetic
material along each
chromosome in a certain order
Homologous Chromosomes
Pairs of chromosomes that
contain similar genes
‒ One from the father,
other is from the mother
meiosis means
-halved
-pulled apart
Diploid, Haploid, and Zygote
Diploid number (2n)
-zygote
– 46 chromosomes
23 pairs of homologous
chromosomes
– Somatic cells (human body cells)
Haploid number (n)
– 23 single chromosomes
– Gametes:
Sperm cell
Ova (oocyte)
Zygote (2n):
– Ovum (23) + Sperm (23)
– 46 chromosomes
23 inherited from each parent
Gene
– Biological unit of heredity
– Sequence of DNA that codes for a specific characteristic (trait)
Alleles (Homozygous & Heterozygous)
Alleles
– Genes that code for traits from chromosome
– Can be identical or different
Homozygous alleles
‒ Alleles that are identical
e.g. BB or bb
Heterozygous alleles
‒ Alleles are different
e.g. Bb
Genotype and Phenotype
Genotype
– An individual’s genetic makeup
– The combination of alleles present
– Indicates homo or hetero for a
e.g. FF, Ff or ff
Phenotype
– characteristics
e.g. freckles vs. no freckles or blue eyes vs. brown eyes
Autosomes and Sex Chromosomes
Autosomes
– Chromosomes 1 to 22
– Chromosomes that contain genes for most of the body characteristics
– In humans: 22 pairs (44 total)
Sex chromosomes
– 23rd pair of chromosomes ( 1 from each parent)
– Determines the sex of an individual
-Females (XX) male (XY)
-Y is smaller then X
Karyotype
– Picture of the chromosomal
make-up of an individual
Punnett square
-possible combinations of
inherited alleles in offspring from male and female parent
-female on top, male on side
-Cap F is dominant
-FF homo dom
-Ff hetero
-ff- home rec
Dominant – Recessive Inheritance
-two phenotypes
-3 genotypes
Dominant allele (D) = dimples, fully expressed
Recessive allele (d) = no dimples, suppressed
Incomplete Dominance Inheritance
-3 phenotypes
-3 genotypes
Heterozygous produce intermediate phenotype
– Neither allele is dominant
– Curly/straight hair example
Upper case C represents allele that codes for curly hair
Lower case c represents allele that codes for straight hair
Example: C (curly) + c (straight) = wavy hair
Codominance Inheritance
-3 genotypes
-3 phenotypes
Both alleles are dominant
– Both dominant alleles are equally expressed – no blending of traits but can carry the trait
Multiple-Allele Inheritance
-6 genotypes
-4 phenotypes
More than 2 types of alleles code for a single trait (eg blood types)
– Dominant alleles are all expressed
– Recessive alleles exhibit dominant-recessive inheritance (suppressed)
Sex-Linked Inheritance
-5 phenotypes
-5 genotypes
Genes on the sex chromosomes (usually the X)
– Dominant allele is completely expressed
– Must keep track of sex
Chromosomal Abnormalities
Damaged, missing, or extra
copies of chromosomes
-eg extra chromosome on 21 is down syndrome
Eyes: Colour in the iris depends on 3 factors
-iris
-Pigment epithelium
-Collagen & cell
density
Polygenic trait – controlled by more than one gene
-both genes + pigment= brown
-only brown melanin pig
-eyes appear blue due to
scattering of light and if no brown pig present
-Shades are due tocollagen & cellulardensity
parent that have blue eyes but carries one of each gene to off can have brown eyes
