Genetics

Have you looked in the mirror recently? Who do you think you look the most like, your mother or father? Your grandma or grandpa?

Heredity These traits are inherited! Heredity is the passing of physical characteristics from parents to offspring

Gregor Mendel Mid 1800’s priest Tended a garden in a monastery His experiments with heredity would influence how we study heredity today

Mendel’s Questions Why do different pea plants have different characteristics? Some grow tall, while others short Some green, some yellow Each of these characteristics are known as traits

Mendel’s Studies He studied traits of peas

Trait

Delving into Mendel! http://www.youtube.com/watch?v=aoVeSncKFAY

Who is 100% one nationality? If you are, you are what’s called a PUREBRED

Mendel started with purebreds, which are organisms that have had the same trait for many generations Example: purebred short pea plants always come from short parents plants

His experiments Started with parents, or P generation Crossed purebred TALL plants with purebred SHORT plants First generation from P generation is called the F1 generation (filial)

GENE Gene: a section of DNA that codes for a trait A chromosome is a chunk of DNA and genes are parts of chromosomes

ALLELE Allele: the different options for a gene Example: attached or unattached earlobes are the alleles for the gene for earlobe shape Two alleles together make a gene or trait

DOMINANT Dominant: an allele that blocks or hides a recessive allele

Recessive Recessive: an allele that is blocked by or hidden by a dominant allele Question: Using purebred crosses, how did Mendel figure out that genes are either dominant or recessive?

GENOTYPE Tt Genotype: A person’s set of alleles (gene options or code for what someone will look like) Genotype is written in letters It is usually the first letter of the dominant allele to make it easier Choose a letter for each of these traits. Write both the dominant and the recessive genotype allele letters Attached Earlobes Freckles Dimples Tongue-roller

GENOTYPE Now, using your letters from before write a genotype for a person without freckles (Freckles are dominant) Write a genotype for a person with freckles

GENOTYPE-HETEROZYGOUS AND HOMOZYGOUS A Heterozygous genotype means an organism has both the dominant and the recessive allele (e.g. Aa) Homozygous recessive means an organism has 2 recessive alleles (e.g. aa) Homozygous dominant means an organism has 2 dominant alleles (e.g. AA)

PHENOTYPE Phenotype: A person’s physical features because of their genotype (appearance!) What you look like (your phenotype) is based on what your genotype is (your genes) What will the phenotype of these genotypes be: WW, Ww, ww (Widow’s Peak dominant over straight hair line) HH, Hh, hh (Hitch hiker’s thumb is dominant over a straight thumb) CC, Cc, cc (Curly hair is dominant over straight hair)

HOMOZYGOUS/HETEROZYGOUS Homozygous: When a person’s two alleles for a gene are the same Heterozygous: When a person’s two alleles for a gene are different You get one allele from your mom and one from your dad. If you get the same alleles from your mom and dad, you are homozygous for that trait. If your mom gave you a different allele than your dad, you are heterozygous for that trait

BUT, not all of genetics follow this simple “Mendelian Genetics”... Sometimes there’s no clear cut dominant and recessive, so therefore scientists came up with “Non-Mendelian Genetics.” Examples: Blood type “Mixed” appearances (like red and white flowers making pink flowers) “Both allele” appearances (such as roan cows!)

Codominance Codominance = when both alleles are expressed (think of co-captains) Example: Roan cow

Codominance Continued Blood type controlled by 3 alleles: A, B and O O is recessive, two O alleles must be present for the person to have type O blood A and B are codominant. If a person receives an A allele and a B allele, their blood type is type AB

Incomplete Dominance Incomplete dominance = both traits are expressed, but are “blended” to make a NEW trait

Incomplete Dominance and Codominance When are they expressed? What do their genotypes look like?

Genotypes of Incomplete and Co-dominance The letters of their genotypes will be different, unlike complete dominance where we have a capitalized and lower case letter (Tt) Example: For roan cows (co-dominance)➔R and W for red and white alleles, roan is RW For pink flowers➔ R and W for red and white alleles, pink is RW

How can you tell if it is NOT the normal, complete dominance, like Tt?  Either will show it is NOT complete dominance: 1) Notice that the offspring is showing a 3rd phenotype.  The parents each have one, and the offspring are different from the parents.  --What is this called? 2) Notice that the trait in the offspring is a blend (mixing) of the parental traits.

Create A Baby Activity Use a coin or a coin app on your phone (as long as you use the app, nothing else on the phone!) to flip heads or tails Heads = dominant allele (capital letter in Mendelian genetics OR first letter in Non-Mendelian genetics) Tails = recessive allele (lowercase letter in Mendelian genetics OR second letter in Non-Mendelian genetics Example: I am looking at hair curliness (Non- Mendelian). I flip heads and my partner flips tails. I get C1 and my partner gets C2. My baby’s genotype is C1C2 (heterozygous) My baby’s phenotype is wavy hair

Create A Baby Activity (Continued) When figuring out the sex of the child: XX = girl XY = boy Flip heads for X and tails for Y. Remember one flip per person When getting to multiple alleles, flip for one of each letter. Example: hair color has 2 different alleles One partner flips for A AND B and the other partner flips A AND B. Result should have two A’s and two B’s **ULTIMATE GOAL = DRAW WHAT YOUR BABY LOOKS LIKE!** ***This is based upon probability or chance of getting either allele***

SO, how did Mendel predict what each generation would look like? He used Punnett squares Grid that looks at genotypes Predicts offspring, or can work backwards to find parents

Which kind of dominance does this Punnett Square show?