Karyotypes and pedigrees
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Karyotypes and Pedigrees. Chapter 14. Chromosome Review. All of an organism’s DNA can be packaged into chromosomes Humans - 23 pairs or 46 total chromosomes Each pair of chromosomes contain genes with 2 alleles (1 from each parent ). Chromosome Review.

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Karyotypes and Pedigrees

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Karyotypes and pedigrees

Karyotypes and Pedigrees

Chapter 14


Chromosome review

Chromosome Review

  • All of an organism’s DNA can be packaged into chromosomes

    • Humans - 23 pairs or 46 total chromosomes

  • Each pair of chromosomes contain genes with 2 alleles (1 from each parent)


Chromosome review1

Chromosome Review

  • All of an organism’s DNA can be packaged into chromosomes

    • Humans - 23 pairs or 46 total chromosomes

  • Each pair of chromosomes contain genes with 2 alleles (1 from each parent)

  • Chromosome Numbers

  • 1-22 autosomes

  • Sex chromosomes “#23”

    • XX – Female

    • XY - Male


Pedigree

Pedigree

  • A pedigree is a chart for tracing genes in a family

    • Phenotypes are used to infer genotypes on a pedigree


Pedigree basics

Pedigree Basics

Circle – Female

Square – Male

Horizontal Line – Mating

Vertical Line – Offspring

Shaded – Has trait

Unshaded – No trait


Human genome

Human Genome

  • Human Genes- human genome contains 20,000 to 30,000 genes.

    • 99.9% of all nucleotide bases are exactly the same in all people

    • Less than 2% of genome actually codes for proteins


Karyotypes

Karyotypes

  • Karyotypes- picture of all chromosomes in a cell for one organism


Creating a karyotype

Creating a Karyotype


Karyotype uses

Karyotype Uses

  • Used to identify certain genetic disorders in which there are extra or too few chromosomes (i.e. Down syndrome 


Identifying gender by karyotype

Identifying Gender by Karyotype

Male

Female


Autosome disorders

Autosome Disorders


Trisomy 21 down s syndrome

Trisomy 21 (Down’s Syndrome)

  • Extra 21st chromosome

  • Male or female (47XX or 47XY)

  • 1/700 births

  • characteristic facial features, short stature; heart defects

  • susceptibility to respiratory disease, shorter lifespan

  • prone to developing early Alzheimer's and leukemia

  • often sexually underdeveloped and sterile, usually some degree of mental retardation.


Patau syndrome trisomy 13

Patau Syndrome (trisomy 13)

  • Extra 13th chromosome

  • Male or female (47XX or 47XY)

  • serious eye, brain, circulatory defects as well as cleft palate.

  • 1:5000 live births.

  • Children rarely live more than a few months.


Edward s syndrome

Edward’s Syndrome

  • Extra 18th chromosome

  • Male or female (47XX or 47XY)

  • almost every organ system affected

  • 1:10,000 live births.

  • Most are stillborn or miscarried

  • Children with full Trisomy 18 generally do not live more than a few months.


Alterations in chromosome structure

Alterations in Chromosome Structure

  • Sometimes, chromosomes break, leading to 3 types of changes in chromosome structure:

    1. Deletion: a portion of one chromosome is lost during cell division. That chromosome is now missing certain genes. When this chromosome is passed on to offspring the result is usually lethal due to missing genes.


Alterations in chromosome structure1

Alterations in Chromosome Structure

- Example: Cri du chat (cry of the cat): A specific deletion of a small portion of chromosome 5; these children have severe mental retardation, a small head with unusual facial features, and a cry that sounds like a distressed cat.


Alterations in chromosome structure2

Alterations in Chromosome Structure

2. Duplication: if the fragment joins the homologous chromosome, then that region is repeated

Example - Fragile X: the most common form of mental retardation. The X chromosome of some people is unusually fragile at one tip - seen "hanging by a thread" under a microscope. Most people have 29 "repeats" at this end of their X-chromosome, those with Fragile X have over 700 repeats due to duplications. Affects 1:1500 males, 1:2500 females.


Alterations in chromosome structure3

Alterations in Chromosome Structure

3. Translocation: a fragment of a chromosome is moved ("trans-located") from one chromosome to another - joins a non-homologous chromosome.

  • The balance of genes is still normal (nothing has been gained or lost) but can alter phenotype as it places genes in a new environment.

  • Can also cause difficulties in egg or sperm development and normal development of a zygote.


Sex chromosome disorders

Sex Chromosome Disorders


Turner s syndrome

Turner’s Syndrome

  • In females,(45XO) sex organs fail to develop at puberty

  • Occurs 1/ 2,000 births

  • http://www.youtube.com/watch?v=ldjb-FR-PKo

Only 1 X chromosome


Triple x syndrome

Triple X Syndrome

  • In females (47XXX)

  • Have normal development

  • Usually taller for their age

  • Occurs 1/ 1,00 births


Klinefelter s syndrome

Klinefelter’s Syndrome

  • In males (47XXY)

  • Sterile, feminine qualities (higher voice, breast development)

  • Little facial hair

  • Taller than average

  • Occurs 1/ 1,000 male births


Jacob s syndrome

Jacob’s Syndrome

  • Male (47XYY)

  • Lead normal lives (most don’t even know they have this)

  • Produce more testosterone  more facial hair, taller

  • Occurs 1/ 1,500 births?


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