Topic 14 Human Genetics

Human Genetics

The science of inherited variations in humans.

How do we Understanding Human Genetics

Karyotyping, pedigrees, and DNA sequencing/ gene mapping.

Pedigree

A 'family tree' that shows inheritance patterns within a family over generations. Important tool for genetic counselors and clinicians.

Polyploidy

Presence of multiple sets of chromosomes; common in plants but lethal in humans and many animals.

From failure of chromosomes to separate during meiosis or fertilization.

Disomy

Cells of normal individuals have two of each kind of chromosome.

Aneuploidies

Abnormalities caused by the presence of a single extra chromosome (trisomy, 2n + 1) or the absence of a single chromosome (monosomy, 2n − 1).

Translocation Down syndrome

Individuals inherit one chromosome 14, one combined 14/21 chromosome, and two normal chromosomes 21; all or part of the genetic material from chromosome 21 is present in triplicate.

Cri du Chat Syndrome

A result of a deletion. Part of the short arm of chromosome 5 is deleted.

Infants have a small head and distinctive cry.

Genomic Imprinting

Expression of a gene in a given tissue or developmental stage is based on whether the gene was inherited from the male or female parent.

May be caused by epigenetic inheritance

Inborn Error of Metabolism

A metabolic disorder caused by the mutation of a gene that codes for an enzyme needed in a biochemical pathway. 1 mutation in 1 gene.

Gene Therapy

Aims to compensate for a defective, mutant allele by adding a normal, therapeutic allele to certain cells.

Still question if its safe.

Genetic Screening

A systematic search through a population for individuals with a genotype or karyotype that might cause a serious genetic disease.

Newborns - detect/treat certain diseases

Adults - make informed reproductive decisions

Human Genome project

Studied genomes of entire populations, extended familiesto identify genes associated with diseases and understand genetic variation.

Karyotyping

illustrates an individual’s chromosome composition. Cells are extracted from the nucleus, spread out, stained, observed and imaged to reveal deviation in number or structure.

Autosomal dominant

First 22 chromosomes, non sex.

Autosomal recessive

sex chromosomes

Human Genome Databases

maps of each chromosome that show the precise location of each gene have been generated. helps determine which gene is associated with the disease.

Non-disjunction

Chromosomes fail to separate at anaphase

Effects of chromosome abnormalities

common in many cancer cells. half of miscarriages contain these.

Turner syndrome

X0 female. Sterile.

XYY Karyotype

Males with extra Y chromosome. Very tall, fertile.

Klinefelter’s Syndrome (XXY)

Males, sterile, small testicles. Low testosterone. Taller, breast enlargement

Abnormal chromosome structure

Breaks in chromosomes are the result of errors in replication or recombination. 4 structural changes; Duplications, Inversions, Deletions, Translocations

Prader-willi syndrome

Genomic imprinting*

Deletion is inherited from the father

Angelmann syndrome

Genomic imprinting*

Deletion is inherited from the mother.

Inborn errors of metabolism examples

PKU, Sickle cell, cystic fibrosis

Types of genetic tests

Amniocentesis - karyotyping of fetus’ cells CVS - cells cultured, then karyotyping