Download Genetics Notes (Class Set)

Name: Class Set
Quiz Date: March 16th Per:
(Edited 3-15-17)
This material can be found in the Our Genes, Our Selves Book (Pages D-3 to D-63) and in your
ScienceSaurus (Pages 115-123). If you would like to check out a textbook, ask Mr. Abraham.
Good BrainPOP videos to watch on this topic include: Genetics, DNA, Heredity, Asexual
Reproduction, Twins and Genetic Mutations.
Think about the main ideas or concepts that we learned about in each of our labs/lessons.
Use words, diagrams, sketches, phrases, bullets, etc. to record the main ideas in the boxes
below. Make the information meaningful for YOUR BRAIN (think about how you learn best).
Investigating Human Traits Lab, Plants Have Genes, Too! and Joe’s Dilemma:
Focus Question: What are characteristics and traits where do they come from and how do they
determine why do I look the way I do?
-Characteristics are features that all organisms of the same species (type) have in common.
Examples in humans include hair color, height, nose shape, hair texture, eye color, etc.
-Traits are specific variations of the characteristics. For example for the characteristic of hair
color some traits include brown, blond, red, black, etc.
-Some traits are very common like being able to roll your tongue. Some traits are very rare red/green
color blindness.
-These traits are passed down through a family which is why family members tend to look similar.
-Genes are genetic pieces of information that are passed from parent to offspring. These traits are
called inherited traits.
-Sometimes diseases and other conditions (like Marfan syndrome) can be passed down from parent
to offspring (inherited).
Copy Cat and Show Me the Genes!: (These two were combined because they are so similar.)
Focus Question: What are different ways an organism can reproduce and how are the chromosomes
passed down from parent to offspring?
-Chromosomes are long strands of genes that can be found in the nucleus of a cell. Chromosomes
and genes are made up of long chains of molecules called DNA.
-Asexual reproduction is when an organism makes an exact copy of themselves without having a
male and female.
-The new organism can be called a clone and has the same genes and traits as the parent.
-In asexual reproduction the chromosomes copy themselves, and then the copies move apart
creating two identical copies of the chromosomes. Then the nucleus splits in two and finally the
cell splits in two creating two exact copies.
-The only chance for genetic variation (a change in the DNA) is if there is a mutation (mistake)
while copying the chromosomes.
-Sexual reproduction is when the female passes on half of her genes and the male passes on half of
his genes to give the offspring a new set of genes.
-Humans have 46 chromosomes (23 pair). When mom makes an egg only 23 chromosomes go into the
egg. Dad only passes on 23 chromosomes to the sperm. When the egg and the sperm meet
(fertilization) mom’s 23 chromosomes pair up with dad’s 23 chromosomes to create the offspring’s
full set of 46 chromosomes.
-Since the DNA is mixed and rearranged there is a great deal of genetic variation (change in the
DNA) from the parents to the offspring. The offspring will not be identical to the parents.
Creature Features and Create a Baby:
Focus Question: How are genes and traits passed down from parents to offspring?
-Sometimes when parents have a trait it is not passed down to their offspring, but will show up in
the third generation. For example Sky’s blue tail was passed down to the offspring, but Poppy’s
orange tail was not. In the third generation some of the offspring had the orange tail. Traits can
skip a generation.
-Genotype is the genetic code of an organism and cannot be seen as they are inside the nuclei of
the cells.
-Phenotype is the set of physical traits of an organism and many can clearly be seen.
-Dominant genes and traits are “stronger” and usually show up in the phenotype. Dominant genes
are written as an uppercase letter.
-Recessive genes and traits are “weaker” and can often be “covered up” or “hidden”. Recessive
genes are written as a lowercase letter.
-An Allele is a pair of genes that determine a trait. Mom will pass down one gene and dad will pass
down the other gene to make the pair.
-If the offspring inherits the dominant genes they will show the dominant trait. If the offspring
inherits the recessive genes they will show the recessive trait. If the offspring inherits one
dominant and one recessive sometimes the dominant trait will be present sometimes it will be a
blend of the dominant and recessive. (This is all very oversimplified.)
Mendel, First Geneticist and Gene Squares:
Focus Question: How are genes and traits passed down from parents to offspring?
-Gregor Mendel was an Austrian Monk that worked with thousands of pea plants and found that
many traits had a 3:1 ratio in the offspring (see the data on D-36). He called the more
common trait the dominant and the lesser seen trait recessive.
-Reginald Punnett also worked with pea plants and noticed this same 1 in 4 or 3:1
ratio. He developed a tool called a Punnett square to predict the ratio of
offspring’s genes based on the parents’ genes. Pages D-41 and 42 walk you
through how to use a Punnett Square.
Poppy (Mom)
-Homozygous is when an organism either has two dominant genes (GG) or
two recessive genes (gg).
-Heterozygous is when an organism has one dominant and one recessive
gene (Gg or gG).
-These traits that show up as a 3:1 ratio are known as Mendelian Traits and are pretty rare in
humans.
Nature and Nurture:
Focus Question: Do our personalities and character qualities come from our genes?
There is a long running debate regarding how much of our personalities, character qualities and
likes and dislikes come from our inherited genes and how much comes from our experiences or
environmental factors. It is clear that both play a role, but there are also some cases where it is
clear that one or the other has a bigger impact.
Hint, Hint, Wink, Wink Question: Made-up-endotisis is a rare disease that causes an
overactive imagination and is recessive. Dad is a carrier (heterozygous) and mom has the
disease (homozygous). What are the chances of the offspring having the disease? Draw the
Punnett square.
Dad
There would be a 2:2 (2 out of 4) (50%) chance of the
offspring having the disease (mm).
Mom
m
m
M
Mm
Mm
m
mm
mm
Sky (Dad)