CHAPTER 4 PATTERNS OF HEREDITY

FOOD FOR THOUGHT… I’m sure you have heard that you look just like one of your relatives. This could be a sibling, parent, or even an ancestor. Think about your family. You may have your mother’s eyes, father’s nose.. Your siblings and you may all share a common trait as well! This does not happen by accident. In fact, these characteristics were chosen to be passed down from your parents to you (offspring). Even if you trace back your heritage to the region of the world where your great ancestors originated, you will find similar characteristics that are common among people

TRAITS A ___ is a characteristic of oneself Some traits are ___, which means they are ___ from parent to offspring. Eye color, skin tone, blood type Some traits are ___, which means they are ___ after you are born Reading, riding a bicycle Some traits are even acquired through interactions and certain events/situations Trauma, skin color (tanning)

WHY DOES THIS HAPPEN? ___ In sexual reproduction, DNA is crossed between both parents. There is a 50/50 chance that a trait will be passed from the father or from the mother… but only one trait can be passed! ___ Heredity is the passing of genes from a parent to its offspring ___ are located on ____ and are the genetic information (DNA codes) that gives you certain traits When an offspring inherits a trait, it is really inheriting that particular ___ for the trait

LET’S GO BACK TO CHROMOSOMES Chromosomes are tightly wrapped strands of ___ Each chromosome contains ___ that can be passed to the ____ There are specific locations on chromosomes where certain genes are placed Since chromosomes are duplicated chromatids (or ____ if we are talking about genes), there are two sets of each trait! This will come in handy later on…

HOW DO TRAITS GET PASSED?

NOT ALL TRAITS ARE IDENTICAL Even though traits get passed from a parent to offspring, there is room for ___. This variation is called an ___ … you’ll hear this word a lot! Let’s say your dad is very tall and you inherited the “tall” gene. This does not mean that you are going to be the same height as your dad. You can be tall, but your actual height can vary thanks to the allele

ALL OUR TRAITS… Being humans, we have 23 pairs of chromosomes (46 total). 23 chromosomes came from your mom and 23 came from your dad The first ___ carry your traits, such as eye color and hair color. The ___ pair determine your gender (boy or girl) Your mother will always pass on an X chromosome. Your dad can pass on an X or Y chromosome XX = girlXY= boy

WHO IS TO BLAME? ____ Austrian monk Mid-1800s Before he was a monk, he attended a university where he studied science and math While fulfilling his monk duties, he took care of the ___. He studied ___ in the garden and observed ___ from parent plants to their offspring

WHAT HE SAW Since all sexually reproducing organisms have two parents, each one can be said to have ___. T = tall t= short T T = both parents passed on the tall allele to this organism t t = both parents passed on the short allele to this organism T t = the offspring inherited a tall allele and a short one Key: we use the same letter to say that it is the same characteristic (height)

WHAT HE SAW Tt Since both letters are the same (meaning the same trait was passed from both parents), these are called TRUE-BRED T t The offspring will take one trait from each parent

LET’S PUT THIS INTO PERSPECTIVE Look at the traits from the parents to the daughter. What traits were passed down? Hair color Eye shape Eye color Nose

LET’S PUT IT INTO PERSPECTIVE Key: B= blonde hair b= brown hair Daughter receives Bb allele.

DOMINANT VS RECESSIVE A ___ allele is the trait that is ___to show up, no matter what it is paired with. This is usually shown by a capital letter A ___allele is the trait that is ___ to show up. This is usually shown by a lower case letter When we pair traits, such as TT or Tt or tt for height in pea plants, there are two ways we can talk about these traits If we are saying that the pairing was TT, Tt, or tt… we are talking about the ___ If we are saying that the height is tall or short, we are talking about the ___

WHAT HE SAW T t T t Tall Short Tall T is the dominant trait

GENOTYPE VS PHENOTYPE Key: B= blonde hair b= brown hair Genotype: Bb Phenotype: blonde hair

CHAPTER 4.2 PUNNETT SQUARES

Punnett Squares help to determine the probability of a trait being passed from parent to offspring

PUNNETT SQUARE B = black b= white

NOW YOU TRY 1.In rabbits, black fur is dominant over white fur. Show the cross of a Bb black male with a bb white female. B b bbbb

NOW YOU TRY 2.Blue eyes are dominant to red eyes in rabbits. Show a EE blue-eyed rabbit crossed with a ee red- eyed rabbit. E eeee

TYPES OF GENES ___- both alleles are the same Dominant-dominant Recessive- recessive ___- alleles are different Dominant-recessive

WORKING BACKWARDS Knowing the possible offspring outcomes, you can figure out what traits parents carry. Ex: blue eyes is a recessive trait (e) to brown (E). Both parents have brown eyes, which means they are homozygous EE or heterozygous Ee. One child has blue eyes.

WORKING BACKWARDS Ex: Ex: blue eyes is a recessive trait (e) to brown (E). Both parents have brown eyes, which means they are homozygous EE or heterozygous Ee. One child has blue eyes. EEEe ee e E E e

WORKING BACKWARDS Rabbits of a certain breed can have offspring that have gray fur (G) or white fur (g). The offspring have a 100% chance of being gray, even though one parent is white. What are the traits of the parents? Gg G G g g

MIXING TRAITS ___ is the mixing of traits. Ex: white fur and black fur parents create gray fur offspring Can have two different dominant traits RW

NOW YOU TRY IT! A blue Blahblah bird (BB) and yellow Blahblah bird (YY) produce offspring that are green. A green Blahblah bird (BY) and blue Blahblah bird produce offspring that are 50% blue and 50% green What are the possible outcomes of two green Blahblah birds?

MEIOSIS CHAPTER 4.3

WHAT IS MEIOSIS? A special kind of cell division that produces cells with _____ ___ are cells that contain ___ the number of DNA needed to produce an offspring, so they combine Egg from female Sperm from male ___- the process of gamete combination

WHAT IS MEIOSIS? Meiosis is ___ as mitosis, meaning that cells ___ in meiosis Cells with a single set of chromosomes are called ___ or gametes (1n) Humans contain 23 unpaired chromosomes before fertilization Cells with ___ of chromosomes are called diploids (2n) In mitosis, the end result is a diploid cell

WHAT IS MEIOSIS? The end result of meiosis is to create more ___ Eggs produce more eggs through oogenesis Sperm produce more sperm through spermatogenesis

THE PROCESSES OF MEIOSIS ___ Chromosomes duplicate and nuclear membrane disappears (2n) ___ Chromosome pairs line up in the center Anaphase I ___ ___and Cytokinesis Cell divides into two daughter cells (2n) Hmm… sounds a lot like mitosis to me!

THE PROCESSES OF MEIOSIS ___ Chromosomes ___ duplicate and nuclear membrane disappears again (2n) Metaphase II ___ Chromatids are pulled apart to opposite ends of the cell Telophase II and Cytokinesis Cell divides into ___(1n)

MEIOSIS

QUESTIONS What is the major difference between prophase 1 and 2? In which phases could genetic variation occur? What is the major difference between metaphase 1 and 2? At which points is your cell a diploid? At which points is your cell a haploid? In which ways did meiosis seem similar to mitosis? In which ways did meiosis seem different than mitosis?

CLARIFICATION ABOUT DIPLOID AND HAPLOID There are two of each color, making a total of four. Whether they are chromatids or chromosomes, the count is still 4 When DNA duplicated, we got 4 chromosomes. The count is still technically 4 This would be considered a diploid There is only one of each color, making a total of 2 chromosomes. Since 2 is half of 4, this would be a haploid. Now we have 2 chromatids. Also haploid because of the number 2

AND AGAIN

CROSSING OVER How do traits get mixed from parents to offspring? Why is it that an offspring can have traits from both parents? ___ occur during prophase I of meiosis. Chromosomes literally ___ and pass genes from one chromosome to the other

MEIOSIS REVIEW Steve is colorblind and carries the trait on the recessive gene (g’). The (‘) represents the colorblindness trait. Colorblindness can only show up on the combination (g’g’). His father carries the gene, but is not colorblind. Steve’s mother also carries the gene. Steve’s sister has traits (Gg). What are Steve’s parents’ genotypes?