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

Heredity heredity – the passing of genetic material from parents to offspring. vocabulary word!

Genetics genetics - scientific study of heredity. vocabulary word!

Gregor Mendel (1822 – 1884) Conducted the first major experiments investigating genetics using pea plants.

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

Mendelian Genetics For pea plants, there appeared to be two options. Mendel called the options traits.

traits - characteristics controlled by genetic material found in the chromosomes. vocabulary word!

Mendelian Genetics In his seed pod color experiments, Mendel would take two “true” breeding plants. –One green parent that only produced green pods –One green parent that only produced yellow pods He would breed these plants together to see the results.

Mendelian Genetics

In the first generation, he noticed all of the pods were green even though there was one yellow parent. He called green dominant He called the other trait recessive because it seemed to disappear or recede.

Mendelian Genetics He then crossed plants from the first generation to see what would happen. About 75% of the offspring had green pods and 25% had yellow. It seemed that the yellow color reappeared.

Mendelian Genetics He concluded that there must be two factors for each trait. –One must come from each parent –Some traits can only be seen if both factors are the same (yellow in this case) –Some traits can be seen even if there is just one dominant factor (green)

Mendelian Genetics –We now call these factors Mendel studied genes.

Chromosomes chromosomes – found in the nucleus and contain genetic information. vocabulary word!

Chromosomes 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. human karyotype

Chromosomes Different species have different numbers of chromosomes:

Genes gene - segment of DNA found in chromosomes that contains instructions for a specific trait. –hair color –eye color –height –chin shape –ear lobes vocabulary word!

Genes We inherit genes from our parents. Each gene has at least two forms. You get one from each parent.

Alleles allele - a different form of a gene. You have 2 or more alleles for each trait you have. One comes from each parent. –Genes come in pairs. –One member of the pair is called an allele. vocabulary word!

Chromosome gene alleles 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 – only one copy is needed for the organism to have the dominant phenotype. It’s represented with a capital letter. curved pinkies PP or Pp free ear lobe FF or Ff straight thumb SS or Ss dimples DD or Dd rolling tongue RR or Rr widow’s peak WW or Ww cleft chin CC or Cc vocabulary word!

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

homozygous- both alleles are dominant or both are recessive. (so you see either two uppercase or two lower case letters. heterozygous – each allele is different. (You will se one capital and one lower case).

Many Genes Can Influence A Single Trait polygenic inheritance - some traits are controlled by more than one gene. There are more than two phenotypes. –eye color –blood type –skin color –height

A Single Gene Can Influence Many Traits Sometimes, one gene can affect multiple traits. –In this tiger and horse, the same gene that causes the white color, also causes the blue eyes.

Environmental Factors The environment can affect how your genes are expressed. –Genes for height but not enough food. –Genes for thin but too much food. –Animals that are different colors based on season.