Human Genetics Genetic Experiment 626

Karyotyping: technique for examining the chromosome make up of an organism shows chromosomes arranged by size: homogulous pairs a way of detecting abnormalities

Karyotyping: chromosomes paired Total of 46 chromosomes Or 23 pair: 22 autosomes, somatic cells, body cells & 1 pair of sex chromosomes XX = female XY = male

Genes located on the sex chromosomes: Sex- Linkage: Genes located on the sex chromosomes: genes found on the x chromosome = x linked genes found on the y chromosome = y linked a gene found on either the x or y chromosomes = sex linked

STOP!!! CK POINT!! Topic: Intro to Human Genetics Identify the following: What is/are: Karyotypes Sex- linked traits

Mutations: any change in the genetic hereditary material of the cell 2 forms: inheritable mutations – occur in the sex cells non inheritable mutations – occur in the somatic cells (autosomes, body cells)

2 Types of inheritable mutations: ADD TO YOUR NOTES!! Chromosomal Mutations And 2. Gene mutations

What are the 2 types of inheritable mutations? STOP!!! CK POINT!! Topic: Mutations 1 What is a mutation? What are the 2 types of inheritable mutations?

Chromosomal Mutations: change in the structure of a chromosome the loss of an entire chromosome or addition of a chromosome Examples Include: a. Nondisjunction

Chromosome Mutation Cont. A. Nondisjunction: failure of chromosomes to separate during meiosis ex. Down syndrome – extra chromosome # 21 Ex .trisomy 18, trisomy 13

Nondisjunction:

Nondisjunction Down syndrome (trisomy 21):

Nondisjunction: Patau syndrome (trisomy 13): serious eye, brain, circulatory defects as well as cleft palate. 1:5000 live births. Children rarely live more than a few months.

Nondisjunction Edward's syndrome (trisomy 18): almost every organ system affected Children rarely live more than a few months.

Other Examples of Nondisjunction: Sex chromosome : Sex chromosome aneuploids XO = Turners Syndrome XXY = Klinefelter Syndrome XXX = Triplo-X Syndrome XYY =Jacob Syndrome

Turners Syndrome: XO individuals are genetically female, however, they do not mature sexually during puberty and are sterile. Short stature and normal intelligence. (98% die before birth)

XXY = Klinefelter Syndrome Male sex organs; unusually small testes, sterile. Breast enlargement and other feminine body characteristics. Normal intelligence.

XXX = Triplo-X Syndrome XXX females. 1:1000 live births - healthy and fertile - cannot be distinguished from normal female except by karyotype

STOP!!! CK POINT!! Topic: Nondisjunction What is Nondisjunction? When does it occur? ( Be Specific) Identify 3 genetic mutations resulting from nondisjunction. What is the cause for each?

Chromosome mutations (structure): translocation – a section of one chromosome is transferred to a nonhomogulous chromosome addition – a portion of a chromosome is added

Chromosome mutations (structure): deletion – a portion of a chromosome is deleted Cri-du-Chat Syndrome (segmental deletion) inversion – order of genes on a chromosome is changed

Chromosomal mutation- Deletion: Example - Cri du chat (cry of the cat): A 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.

In summary Chromosomal Mutations: Chromosomal abnormalities can cause serious mental or physical disabilities, Structure of the chromosome has been compromised The number of chromosomes is incorrect

STOP!!! CK POINT!! Topic: Mutations 2 1. Identify 4 structural chromosomal mutations. How are each of the 4 chromosomes mutated? 3. What is Turners Syndrome?

Gene Mutations Point Mutation – the substitution, addition, or removal of a single nucleotide substitutions, 1 nucleotide in a codon is replaced with a different nucleotide, resulting in a new codon. sickle cell anemia (also called sickle cell disease) is a point mutation substituting Adenine for Thymine in a single DNA codon,

Gene Mutations Cont. Frame Shift Mutation -the addition or deletion of a single nucleotide causes the remaining codons to be incorrectly grouped Addition/removal – a single nucleotide is added or removed Addition and Deletion Mutations

sickle cell

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Characteristics of Mutations: most are harmful to the organism they are random most are recessive traits Can be beneficial to the organism when the mutation helps the organism to adapt to the environment.

Mutagenic Agents: radiation - x-rays, radioactive isotopes, cosmic rays, ultraviolet rays chemicals – saccharin, nitrates, carcinogens

Human Genetic Traits & Disorders X- linked Traits: traits controlled by the female sex chromosome symbolized by a character on 1 of the chromosomes XX’ X’ carries the trait The female = the carrier The trait is not visible in the female

Examples of Sex linked traits: X- linked Ex. Hemophilia –blood disorder in which blood does not clot properly Ex. Color blindness – cannot distinguish between red and green

X-linked traits cont. Symbols for constructing a Punnett square (sex-linked trait) XX normal female XY normal male X’X carrier female X’Y male with hemophilia http://www.macmed.ttuhsc.edu/Morgan/bleedingdisorders/pages/newpage26.htm Know These!!!!

Ex. Hemophilia Hemophiliac male x carrier female Genotype Phenotype

Hemophilia cont. Normal male x female carrier Genotype Phenotype

2 or more alleles for a particular trait Multiple Alleles: 2 or more alleles for a particular trait alleles are expressed as codominant ex. Blood types

Human Blood Types: Phenotype Genotype A IAIA, IAi B IBIB, IBi AB AB O ii

Blood Types & Punnett Squares; What are the possible outcomes for a heterozygous A blood type crossing with a homozygous B blood type? Genotypes Phenotypes

Blood Type Cont. Construct a punnett square showing a cross b/w a blood type O person with a heterozygous B blood type person Genotype Phenotype

Why? THINK! Raise your hand to answer… WHY Blood typing important?

RBC

agglutination

Put your skills to the test! Look at the handout provided: “Using Blood tests to Identify Babies”

Polygenic Traits: traits controlled by 2 or more alleles expressed as incomplete dominance ex. Eye color, height, and skin color This pattern of inheritance is identified has a wide range of phenotypes (skin & hair color).

How is multiple alleles different from polygenic traits? (look in your THINK… How is multiple alleles different from polygenic traits? (look in your notes!)

Go SU!!

Genetic Disorders: Genetic screening or studying Karyotypes can show possible genetic disorders Amniocentesis – Karyotyping and analyzing amniotic fluid for fetal cells Chorionic villi sampling – piece of the placenta that is studied for genetic abnormalities Ex. PKU: a genetic disorder that does not allow the baby to breakdown phenylalanine , can cause severe brain damage Can be detected and eliminated with special diets

STOP!!! CK POINT!! Topic: Genetic Disorders What is the difference among: Multiple Alleles Sex-Linked Traits Polygenic Traits What is amniocentesis?

Disorders associated with Genetics: Cystic Fibrosis Tay - Sacs Disease Phenylketonuria (PKU) Huntington’s disease Albinism

Cystic Fibrosis Symptoms Mucous clogs the lungs and pancreas Usually do not survive into adulthood White population most effected

Tay-Sachs Symptoms: Deterioration of the nervous system Usually do not survive adulthood European descents most effected

Failure of the brain to develop during infancy PKU Failure of the brain to develop during infancy If untreated, death in early childhood Controlled by diet!!

Huntington’s Disease Carried on an autosome (Dom) Symptoms: Forgetfulness Appears in 30’s-40’s Loss of muscle control Uncontrollable muscle spasms Mental illness death

In your pkt: Get into your groups: > 1 min. Get owl text books Same place as yesterday Turn to pg 91-92 Begin answering questions Popsicle sticks!!