Human Heredity

There are traits that are controlled by one gene with 2 alleles There are traits that are controlled by one gene with 2 alleles. Often, one is dominant and the other is recessive Example: widow’s peaks and dimples.

For example: blood types and skin color in humans. Some traits are controlled by a gene with multiple alleles – 3 or more for a single trait. For example: blood types and skin color in humans.

There are 44 chromosomes that we call autosomal chromosomes. However, there are 2 chromosomes that determine our sex and we call them sex chromosomes. These 46 chromosomes all carrier genes on them that determine our traits.

Out of our 23 pairs of chromosomes, 1 pair is the sex chromosomes (X and Y). Female = XX Male = XY

Question: What is the probability that your parents will have a boy or girl? XY (dad) x XX (mom) X Y Phenotype: 50% boy 50% girl X XX XY Genotype: 50% XX 50% XY X XX XY

Question? If my parents have 5 boys in a row, what is the chance they will have a girl the next time? 50%

Sex-linked gene: Some traits are carried on the sex chromosomes. Genes on the X or Y chromosomes are sex-linked genes. These traits are passes on from parent to child. Sex- linked genes can be recessive or dominant. MALES are more likely to have a sex-linked trait because they only have ONE X and Y. The allele is USUALLY on the X chromosome. Ex. colorblindness, hemophilia, hairy ears, muscular dystrophy

Are you colorblind? What numbers do you see?

Carrier – person who has one recessive allele and one dominant allele for a trait or heterozygous for that trait (only women can be carriers). Example Hemophiliac carrier XHXh Colorblind carrier XBXb

Xb Y XB Xb Sex linked Punnett Squares: Question: What is the probability that a carrier female and a colorblind male will have a girl who is colorblind (b = colorblind, B = normal)? Xb Y Phenotype: 25% normal boy 25% colorblind boy 25% normal girl 25% colorblind girl XBXb XBY XB Xb XbXb XbY

Try this one on your own Question: What is the probability that a homozygous (normal vision) female and a colorblind male will have a girl who is colorblind (b = colorblind, B = normal)?

Xb Y XB XB Parents: XBXB x XbY XBXb XBY XBXb XBY Phenotype: 50% normal girls 50% normal boys XBXb XBY XB XB XBXb XBY

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Pedigree Simply a family tree describing the interrelationships of parents and children across the generations Males – square Females – circle Past and future Genotype and phenotype Sex-linked or autosomal

Carriers do not show that particular trait phenotypically but have a chance to pass the trait on to their child. Carrier – half colored

Reading a Pedigree Task 1: Genotyping a pedigree chart Task 2: Take out your pedigree sheet. Lets do the first one together. Do # 2.

Sex-linked-Practice on your own: What is the probability of a female carrier of hemophilia and a normal male having a boy with hemophilia (X-linked recessive)? What is the probability of a man with hairy ears and a woman having a son with hairy ears (Y-linked recessive)? What is the probability of a carrier woman and a male with muscular dystrophy having a girl with muscular dystrophy (X-linked recessive)?

Genetic Engineering

Cloning – Ch. 13 Donor cell taken from original animal Fused with egg cell with no nucleus Fused with electric shock Dolly First mammal cloned Offspring genetically IDENTICAL to parent/donor

CC (Copy Cat) http://www.msnbc.msn.com/id/3076908/

DNA Fingerprinting Analyze sections of DNA that have little or no known function Sections that vary widely from one individual to another Positive ID has similar marker to mother AND father Remember you get your chromosomes from both your mom AND your dad

Uses gel electrophoresis – gel setup between two poles; positive charge on one end and negative on the other Amino acids have different charges and travel along the gel depending on that charge Figure 14-18: which suspect matches the evidence?

Human Genome Project Scientists working on full set of chromosomes/DNA sequence of humans Look at haploid set of chromosomes Human genome - ~3 billion base pairs

Stem Cells Unspecialized cells with the potential to become a variety of cells Taken from embryos Moral and ethical objections Immune system may reject stem cells Mouse cells to date