Heredity Inherited Traits Have you ever wondered….. Why do people have babies? Why do dogs have puppies? Why do birds have baby birds? Why do seals have pups?

We inherit our traits from our parents!

What is a trait? A trait is any notable feature or quality in a person or organism. Physical traits Behavioral traits Some traits can be influenced by our environment or the things we do. For example: hair color skin color predisposition for certain medical conditions

What defines our traits? Our Genes determine our traits. NO, NOT YOUR BLUE JEANS! The genes located on the chromosomes that are found in the nucleus of our cells… We inherited these from our parents

Let’s look at some of the dominant traits listed below. Free earlobes Cannot fold tongue up Clockwise hair whorl Bushy, thick eyebrows Brown Eyes Dark Hair Dimples Curly Hair Freckles Dark eyebrows Turned up nose Widow’s peak Straight little finger Can roll tongue Straight little finger

If you have a dominant trait, that means you inherited the trait from at least one of your parents. For instance Ff or FF for freckles. F + f = freckles F + F = freckles Alleles for dominant traits are usually represented with a capital letter.

If you have a recessive trait, that means you had to inherit the trait from both of your parents. For instance ff for no freckles. f + f = no freckles Alleles for recessive traits are usually represented with a lower case letter.

The Mask Dominant genes mask, hide, or overpower the trait of the recessive gene. The recessive gene is still present, but it is not expressed….. It does not show up in the form of a trait that can be seen or noticed by others. There are other traits that occur in degrees such as the color of carnation flowers. A white flower and a red flower can produce a pink flower.

Gregor Mendel The Father of Genetics Click the picture to link to Mendel’s biography.

Gregor Mendel, 1863 The Father of Genetics While studying pea plants, a monk named Gregor Mendel discovered that traits are passed from parent to offspring, that traits can be hidden for a generation, and that hidden traits can reappear in later generations. He theorized that the plant received an allele from each parent. The allele was the form of a gene and produced the trait. He created the Punnett Square, a mathematical square to predict the possible traits of offspring from certain parents.

Punnett Square Let’s work one on the board together for the freckles. If mom has FF and dad has ff, what happens? F mom is Ff and dad is Ff, what happens?

Homozygous vs. Heterozygous Homozygous means the alleles for the trait are the same : FF or ff Heterozygous means the alleles for the trait are different : Ff

Where do the alleles come from? Alleles come from the genes that are located on the chromosomes inside the nucleus. Chromosomes are made of long molecules of DNA representing thousands of genes Build a DNA molecule. Click here to learn more about DNA, genes, and proteins. Click here to learn more aboutDNA genes, and proteins. Francis Crick and James Watson figured out how a DNA molecule fit together. Click on the underlined names to meet them! Francis Crick James Watson

How are genes passed from parent to child? Through reproduction. The child receives a set of chromosomes from the mom and a set of chromosomes from the dad. Humans have 46 chromosomes or 23 pairs of chromosomes. Other organisms have different numbers of chromosomes.

Each organism received its genes from its parents. Let’s use a critter to explore…. This critter has 8 chromosomes. Let’s see if you can determine the traits a critter would have if it had the chromosomes and alleles in your bag. Yellow chromosome BLUE green eye color Pink chromosome BROWN orange spots or not Orange chromosome PURPLE yellow skin color Purple chromosome RED lt blue curly tongue

Now lets watch meiosis Demonstration by Mrs. McNeill.

Mrs. McNEill

4 Daughter Cells from One Parent Cell HALF THE CHROMOSOME NUMBER FOR EACH CELL!!!!

4 Daughter Cells from One Parent Cell HALF THE CHROMOSOME NUMBER FOR EACH CELL!!!!

Sex Cells are Haploid or Half The gametes are the sex cells of the parents. When formed they undergo meiosis. In the process, the chromosomes are duplicated, then separated and packaged as separate sets in the sex cells. If this were not the case, the number of chromosomes would double every time a new organism was created.

Meiosis

More meiosis

Cells dividing in meiosis

Mrs. McNeill’s Critters underwent Meiosis Duplicate, split, make 4 new cells Now 4 daughter cells or 4 sex cells Does each daughter cell have the same alleles for the traits?????

YOUR TURN! You will not duplicate yours, just separate them so you have 2 sets of half. The left side of the table will pick one half to simulate meiosis. The right side of the table will pick one half to simulate meiosis. Now put the two chosen cells together. Do not plan, put them together randomly.

Congratulations! CONGRATULATIONS…..you have a new critter! Draw a baby picture of your critter. Yellow chromosome BLUE green eye color Pink chromosome BROWN orange spots or not Orange chromosome PURPLE yellow skin color Purple chromosome RED lt blue curly tongue

Quiz How did you know which traits to draw? Where are chromosomes located? Do all organisms have the same number of chromosomes? Is there only one gene on a chromosome or many? Explain dominant and recessive. Explain heredity.

Homework Ask your family to show you their traits. Can they roll their tongues? Do they have dimples? What other traits will you notice? Whether through sexual or asexual reproduction, traits are passed from the parent to the offspring on the genes that are inherited.