Inheritance & Human Genetic Patterns

Chapter 12-13

Thomas Hunt Morgan Early 1900’s Used fruit flies, Drosophila

melanogaster to identify genetic patterns.

Observed that only male fruit flies had white eyes

WHY??

Linkage groups

A group of genes located on one chromosome.

These genes are usually inherited together.

Example: Fruit flies have 4 pairs of chromosomes

& four linkage groups. How many linkage groups do humans

have?

Sex Determination

Sex Chromosomes X & Y Located in 23rd position (human) XX – female XY - male

Autosomes All other chromosomes

Sex Linkage

Traits that are linked to sex chromosomes.

Gene Maps

Show the relative locations of each known gene on an organisms’ chromosome.

Mutations

Change in DNA Germ cell mutation

Occurs in gametes Do no affect the organism May be passed on offspring

Somatic cell mutation Occurs in body cells Not passed to offspring

LETHAL MUTATIONS: cause death usually before birth

Gene mutations

Involve a single nitrogen base or larger segment of DNA. Point Mutations

Substitution, addition, or removal of a single nitrogen base

Mutagen Environmental factor that

damages DNA Ex. Carcinogens, tobacco,

tars, UV radiation

Chromosome Mutations

Deletion Loss of a piece of chromosome

Inversion Chromosome section breaks off &

reattaches in reverse orientation.

Chromosome Mutations cont…

Translocation Chromosome section

breaks off & reattaches to another, non-homologous chromosome

Nondisjunction Failure of a

chromosome to separate during meiosis.

Results of Nondisjunction

Monosomy Zygote with 45 chromosomes Turners Syndrome (XO)

Trisomy Zygote with 47 chromosomes Down Syndrome (Trisomy 21) Klinefelters Syndrome (XXY)

Trisomy 21

Genetic Traits & Disorders

Single Allele Traits (dominant) Huntington’s Disease,

Achondroplasia (Dwarfism), Cataracts, Polydactyly

Single Allele Traits (recessive) Albinism, PKU, Cystic Fibrosis,

Hereditary deafness, Sickle cell anemia

Genetic Traits continued…

X-linked Traits Colorblindness, hemophilia, muscular

dystrophy, ichthyosis simplex Multiple Allele Traits

Blood Types Polygenic Traits

Skin, hair, & eye color; foot size, nose length, height

Sex-influenced Traits Male pattern baldness

Detecting Human Genetic Disorders

Genetic Screening Examination of person’s genetic

makeup Genetic Counseling Amniocentesis

Removal of amniotic fluid from mother Chorionic Villi Sampling

Villi contain same genetic makeup of fetus

Continued…

Karyotype Picture of an organisms’ chromosomes

Ultrasound Bouncing sound waves off fetus to

create an image Pedigree

Family record that shows how traits are inherited over several generations

Pedigree

DNA Technology

Genetic Engineering Used to identify genes for specific traits Transfer genes for a specific trait from

one organism to another organism. Uses of DNA Technology

Cure diseases Treat genetic disorders Improve good crops

Transplanting Genes

Isolate a gene (ex. Insulin) Produce recombinant DNA

A combination of DNA from 2 or more sources.

Clone DNA Allow bacteria time to reproduce

Transgenic animal: A host organism receiving recombinant DNA

The Human Genome Project

Goals: To determine the

nucleotide sequence of the entire human genome (approx. 3 billion nucleotide pairs or 100,000 genes)

To map the location of every gene.

Gene Therapy

Treating a disorder by introducing a gene into a cell or by correcting a gene defect in a cell’s genome.