It ’ s in the Genes

1. It’s in the Genes Our blueprint for the body

2. Genes and Chromososmes • A gene is a unit of hereditary material • Contains coded information and instructions which direct the development of every cell in the body • Like a blueprint of how the body will function

3. A gene is a segment of DNA • This DNA tells cells how to make a protein • Proteins are the building blocks of our body • There are about 100,000 genes in the human body • Genes are found on thread-like structures, called chromosomes

4. Chromosome

5. Chromosomes • Chromosomes are found in the nucleus of the cell • They exist in pairs • Humans have 23 chromosome pairs • At the time of conception, each parent contributes one gene and one chromosome from each of the pairs • So our cells have 2 copies of each chromosome, one from each parent.

6. Human Chromosomes

7. Traits • Genes and chromosomes from each parent combine to determine which traits the offspring inherits • At each gene location site on the chromosome, there are two variations of the gene, called alleles • If they are identical, the individual is homozygous • If they are different, heterozygous.

8. More on alleles • Alleles are either dominant or recessive • The dominant allele in the pair determines the trait • E.g. Eye color genes. Brown alleles are dominant over lighter colors. In a pair of alleles with 1 blue and 1 brown, the brown will overshadow the blue and the person will have brown eyes

9. Punnett Square • Maps the genes of the parents • Dominant alleles shown by a capital letter and recessives by a small. • Combinations of the dominant and recessive genes result in the traits • One trait does not affect another • We will be doing an exercise later with a Punnet square

10. Mutations • Mutations are changes in the gene. • Like a misspelling in the code for a protein that can be passed from one generation to the next • Some mutations are not harmful • Some mutant genes function improperly and cause a disorder, malfunction, or malformation • E.g. Cystic fibrosis or Marfan’s

11. Mutations Some mutations can occur spontaneously and thus can appear for the first time in a family People have no control over which genes they pass along to their offspring However, when a person is affected with a genetic disorder that causes illness or disability, they may want to consider whether they pass that gene along.

12. Congenital Disorders • Congenital disorders are caused by damage to a developing fetus. • Can be the result of genetic abnormalities or mutations, the uterine environment or chromosomal abnormalities (Down’s Trisomy 21) • Congenital disorders are not necessarily genetic.

13. Types of congenital disorders • Congenital physical anomaly is an abnormality of the structure of a body part (clinodactaly) • Congenital malformation is an anomaly that is problematic • Birth defect is a congenital anomaly evident at birth that is problematic (spina bifida) • Genetic disorders are all congenital, but may not show until later in life. • Single, multiple gene or chromosomal defects

14. Teratogens • Any agent that can disturb the development of an embryo or fetus. • A number of medications can cause birth defects (thalidomide was the most famous) • Alcohol, ACE inhibitirs, sulfas, statins, phenytoin, anti-cancer drugs, radiation • Avoidance of drugs and alcohol in pegnancy. Smoking not a teratogen, but can cause LBW • Pregnancy Category Ratings

15. Dwarfism • Person of short stature • Can be caused by over 200 medical conditions • Characteristics of individuals vary widely • Disproportionate: one or more body parts being large or small in comparison to normal adult humans • Proportionate dwarfs are small all over

16. More kinds of dwarfism • Achondroplasia: 70% of dwarfs. • Bone growth disorder • Short limbs, long trunk, large head with characteristic facial features • Pituitary dwarfism is caused by a growth hormone deficiency.