It ’ s in the Genes Our blueprint for the body

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

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

Chromosome

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

Human Chromosomes

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

More on alleles Alleles are either dominant or recessiveAlleles are either dominant or recessive The dominant allele in the pair determines the traitThe 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 eyesE.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

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

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

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.

Congenital Disorders Congenital disorders are caused by damage to a developing fetus.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)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.Congenital disorders are not necessarily genetic.

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

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

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

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