JH-KEADLE Genetics and Heredity

Learned Behavior Inherited Trait Look at he list below and decide if each is a learned behavior or an inherited trait using tools curly hair bright feathers where to hunt for food what food tastes good blue eyes building a shelter

Prokaryotes and Eukaryotes Prokaryotes and eukaryotes both have DNA

Prokaryotes Eukaryotes protists fungi plants animals archaebacteria bacteria

Goals We will focus on genetic material and how it is passed from one generation to the next. All living organisms reproduce and pass traits to their offspring

Heredity The process in which traits pass from parents to offspring

Genetics Scientific study of heredity

Traits Traits characteristics controlled by genetic material found in the chromosomes Phenotype – what you can see Genotype – genetic code for a trait

Traits Where do traits come from? parents

Chromosomes Chromosomes are found in the nucleus Chromosomes are made of DNA

Chromosomes The piece of yarn on your desk is a model of the amount of genetic material inside each one of your cells. Human cells have 46 chromosomes (except the sperm and egg) and if they were connected and stretched out, they would be about 2 meters long Other organisms have different numbers of chromosomes

Chromosomes

Chromosomes This is a karyotype of human chromosomes

DNA DNA is an organic compound called deoxyribonucleic acid

DNA DNA is made up of four nitrogenous bases Adenine (A) Guanine (G) Cytosine (C) Thymine (T) When linked properly, these connected bases create a shape called a double helix (spiral staircase)

DNA A G T C C A G T A A C A T T T C A G G T Guanine (G) always pairs with Cytosine (C) Thymine (T) always pairs with Adenine (A) A G T C C A G T A A C A T T T C A G G T

Genes Segment of a DNA molecule that contains information for a specific trait hair color eye color height chin shape ear lobes

Alleles An allele is a different form of a gene Genes come in pairs One member of the pair is called an allele You have 2 or more alleles for each trait you have

Chromosome gene alleles smallest to largest DNA smallest to largest gene→ DNA→ chromosome→ nucleus

Dominant and Recessive Alleles Even though you get at least 2 alleles for each trait, only one shows The dominant allele will be the one that you see The recessive allele will be hidden

Dominant Allele If the dominant allele is present in the gene pair, the organism shows the dominant phenotype represented with a capital letter curved pinkies PP or Pp straight thumb SS or Ss rolling tongue RR or Rr free ear lobe FF or Ff cleft chin CC or Cc widow’s peak WW or Ww dimples DD or Dd

Recessive Allele Allele that is hidden if the dominant allele is present Both alleles in the gene have to be recessive to see the recessive phenotype Represented with a lower case letter non -rolling tongue rr straight pinkies pp curved thumb ss attached ear lobe ff smooth chin cc no widow’s peak ww no dimples dd

summary Within the nucleus, genes occur in pairs. A gene is a segment of DNA located on each chromosome Each gene has a particular form called an allele

summary An allele can be either dominant or recessive If a dominant allele of a gene is present, the dominant trait will appear in an organism In order for a recessive trait to appear, both alleles of a gene must be recessive

Gregor Mendel (1822 – 1884) Father of genetics Lived in Austria Became a monk studied genetics using pea plants

Mendelian Genetics Mendel looked at several traits in pea plants pod shape flower color plant height

Mendelian Genetics Mendel termed traits as dominant or recessive Punnett square – a chart used to predict what traits the offspring of two parents would have

Punnett Square To set up a Punnett Square, decide which trait is dominant dominant trait = capital letter recessive trait = lower case letter homozygous = two capital or two lowercase (PP or pp) heterozygous = one capital and one lower (Pp)

P P p p Pp Pp Pp Pp Punnett Square Use P for purple flower color Use p for white flower color homozygous P P p Pp Pp homozygous p Pp Pp

P p P p PP Pp pp Pp Punnett Square Cross two heterozygous plants

Results of the Punnett Square Each individual from the Punnett Square will have a genotype and a phenotype Genotype – what the genes are Phenotype – what it looks like

Results of the Punnett Square Punnett Results Genotype Phenotype PP Homozygous dominant Purple Flowers Pp Heterozygous pp Homozygous recessive White Flowers

Punnett Square Practice A dog breeder is mating a brown heterozygous lab to a black homozygous lab. Brown is dominant. Set up a Punnett Square and decide what percent of the offspring will be black and brown. ? X =

b B b Bb bb Bb bb b Bb One parent is heterozygous brown B = brown b = black Bb One parent is heterozygous brown One parent is homozygous black bb b B b Bb bb Bb bb b

Bb Bb Bb Bb bb bb bb bb 50% are brown, 50% are black brown brown black Results of Cross Phenotype Genotype Bb Bb brown Bb Bb brown bb bb black bb bb black 50% are brown, 50% are black

Punnett Square Practice A cattle breeder wants to get rid of horns in his cattle herd. Polled (no horns) is a dominant trait. Horned is recessive. If he bred a heterozygous bull to heterozygous cows would he get all polled calves? Set up an Punnett Square and answer the question. ? = X

h H H HH Hh Hh hh h Hh Hh H = polled h = horns One parent is heterozygous horned Hh h H H HH Hh Hh hh h

HH HH Hh Hh Hh Hh hh hh 75% are polled, 25% are horned polled polled Results of Cross Phenotype Genotype HH HH polled Hh Hh polled Hh Hh polled hh hh horned 75% are polled, 25% are horned

Incomplete Dominance X = Some traits are not dominant or recessive These traits will blend when heterozygous You can use a Punnett square and will have 3 genotypes instead of two X =

Punnett Square Practice In purple people eaters one eye is homozygous dominant, two eyes is homozygous recessive, and three eyes is heterozygous. The number of eyes in an incomplete dominant trait. What would the offspring look like from a homozygous recessive purple people eater and a homozygous dominant purple people eater? Set up a Punnett Square and find the genotypes and phenotypes of the offspring.

E E e Ee Ee Ee Ee e EE = one eye ee = two eyes Ee = three eyes One parent is homozygous dominant One parent is homozygous recessive EE ee E E e Ee Ee Ee Ee e

Ee Ee Ee Ee Ee Ee Ee Ee 100% three eyed 3 eyes 3 eyes 3 eyes 3 eyes Results of Cross Phenotype Genotype Ee Ee 3 eyes Ee Ee 3 eyes Ee Ee 3 eyes Ee Ee 3 eyes 100% three eyed

Polygenic Inheritance Some traits are controlled by more than one gene There are more than 2 phenotypes eye color blood type skin color height

Genetic Mutations Gene undergoes a change An error in the copying of the DNA Some mutation are beneficial Some mutation are harmful

Chromosome Disorders Sometimes the incorrect number of chromosomes occur This is produced by mistakes during meiosis A change in the total number of human chromosomes (46) usually leads to death before the baby is born However, some additions and subtraction in the chromosome number do survive

Down’s Syndrome Extra chromosome at pair 21

Environmental Factors The environment can effect how your genes are expressed Genes for height but not enough food Genes for thin but too much food