Lab 5 Human GeneticsLab coordinator: Dr. Ana Medrano

Office: 108D STL

Email: introbio@uh.edu

TA: Your Name

Agenda

Today Quiz 3 75% Lab 3 Genetics & 25% Lab 5 Human

Genetics

Lab- 5 Human Genetics

Next week (Feb 23 -27) Quiz 4 75% Lab 5 Human Genetics & Lab 4 Writing a

Lab Report

Lab-4 Writing Lab Report

Chromosomes

Chromosomes are made of DNA.

Each contains genes in a linear order.

Human body cells contain 46 chromosomes in 23 pairs one of each pair inherited from each parent

Chromosome pairs 1 22 are called autosomes.

The 23rd pair are called sex chromosomes: XX is female, XY is male.Gene for sickle cell disease

(chromosome 11)

Gene for cystic fibrosis (chromosome 7)

Autosomal and Sex Chromosomes

Autosomes are the first 22 homologous pairs of human chromosomes that do not influence the sex of an individual.

Sex Chromosomes are the 23rd pair of chromosomes that determine the sex of an individual.

Karyotyping

A karyotype is the number and appearance of chromosomes in the nucleus of a eukaryotic cell.

The term is also used for the complete set of chromosomes in a species, or an individual organism

Chromosomes

p

Centromere

q

Chromosome 5

G-banding of Chromosomes

G-banding is obtained with Giemsa stain following digestion of chromosomes with trypsin.

It yields a series of lightly and darkly stained bands - the dark regions tend to be heterochromatic, late-replicating and AT rich.

The light regions tend to be euchromatic, early-replicating and GC rich.

This method will normally produce 300-400 bands in a normal, human genome.

How to make karyotype

Scientists prepare metaphase preparation of banded(stained) chromosomes and take the picture of it.

They match homologous chromosomes by size, length of arms, and location of the centromere.

Cytogenetics

If you want to become cytogenetist https://www.youtube.com/watch?v=l3jY1T4FZDY

The online exercise http://learn.genetics.utah.edu/content/chromosomes/k

aryotype/

X and Y chromosomes

Males have one X and one Y chromosome.

Females have two X chromosomes.

In females, one of the X chromosome is turned off randomly during development. Therefore, in both male and female there is only one

active X chromosome.

The inactive X chromosome in female somatic cell is also called Barr Body

Barr Body

is the inactive X chromosome in a female somatic cell.

No such body is found in male cells.

Only one X chromosome remains active in females and the other X-chromosomes is condensed giving the Barr body

Mendelian

Inheritance in

Humans

Observable Human Characteristics

Some traits are controlled by genes that pass from parent to child. Others are acquired through learning. But most are influenced by a combination of genes and environmental factors.

Several human traits do follow Mendels law of segregation.

We will observe several traits today in the lab.

Observable Human CharacteristicsSome examples

Earlobe attachment

Tongue Rolling

Dimples

Widows peak

PTC tasting

Genetics Traits

Pedigree Chart

A pedigree is a chart of the genetic history of family over several generations.

Scientists or a genetic counselor would find out about your family history and make this chart to analyze.

Symbols and Rules:

Male = Female =

Affected = Unaffected =

Link parents together with a line and then make a vertical line to connect to offspring.

Interpreting a Pedigree Chart

1. Determine if the pedigree chart shows an autosomal or X-linked disease.

If most of the males in the pedigree are affected the disorder is X-linked

If it is a 50/50 ratio between men and women the disorder is autosomal.

Example of Pedigree Charts

Is it Autosomal or X-linked?

Interpreting a Pedigree Chart

Determine whether the disorder is dominant or recessive.

If the disorder is dominant, one of the parents must have the disorder.

If the disorder is recessive, neither parent has to have the disorder because they can be heterozygous.

Example of Pedigree Charts

Dominant or Recessive?

Example of Pedigree Charts

Dominant or Recessive?