Bell Ringer 12/2/13Bell Ringer 12/2/13Create a vocab chart on a Create a vocab chart on a

new sheet of papernew sheet of paperWord Definition More informationHeredity traitgeneticsgametefertilization

GeneticsGenetics

http://www.youtube.com/watch?v=B_PQ8qYtUL0

Genetics Using Genetics Using Punnett Squares Punnett Squares

Early GeneticsEarly Genetics• The study of geneticsThe study of genetics began with began with

observations made by observations made by Gregor Mendel.Gregor Mendel.

• After noticing that the After noticing that the flowers his pea plants flowers his pea plants were either violet or were either violet or white, Mendel began to white, Mendel began to study the segregation study the segregation of heritable traits. of heritable traits.

Between 1856 and 1863 he cultivated and tested at least 28,000 pea plants.

Remember that Mendel worked almost 150 years ago when nobody knew about genes or even the structures (chromosomes) that carry genes.

Here are some traits observed by Mendel:

Mendel’s ConclusionsMendel’s Conclusions1.1. Law of segregation – Law of segregation –

– every individual has 2 forms (alleles) of a every individual has 2 forms (alleles) of a gene and when sex cells (gametes) are gene and when sex cells (gametes) are produced each gamete produced produced each gamete produced receives one of these allelesreceives one of these alleles

2.2. Law of Independent AssortmentLaw of Independent Assortment– Genes of individual traits are inherited Genes of individual traits are inherited

independently of each otherindependently of each other– Ex: gene for eye color is independent of Ex: gene for eye color is independent of

hair color genehair color gene

Lets consider a single Lets consider a single gene…gene…

• A gene carries A gene carries information that information that determines your determines your traits. traits. Traits are Traits are characteristics you characteristics you inherit from your inherit from your parents.parents.

• Genes are located in Genes are located in chromosomes.chromosomes.

• Chromosomes come Chromosomes come in pairs and there are in pairs and there are thousands, of genes thousands, of genes in one chromosome. in one chromosome.

Continued…Continued…• In humans, a cellIn humans, a cell’’s s

nucleus contains 46 nucleus contains 46 individualindividualchromosomes or 23 pairs chromosomes or 23 pairs of chromosomes.of chromosomes.

• Half of the chromosomes Half of the chromosomes come from one parent come from one parent and half come from the and half come from the other parent. other parent.

This is a human karyotype representing the 23 pairs of chromosomes in a male Here is the

detailed structure of a chromosome

DefinitionsDefinitions• Allele-Allele- discrete version of the same gene discrete version of the same gene • Genotype-Genotype- the the ggenes of an organism for enes of an organism for

one specific trait one specific trait • Phenotype-Phenotype- the the pphysical appearance of a hysical appearance of a

trait in an organismtrait in an organism

DefinitionsDefinitions• Dominant Dominant trait refers to a genetic feature trait refers to a genetic feature

that that ““hideshides”” the recessive trait in the the recessive trait in the phenotype of an individual. phenotype of an individual.

• The term "The term "recessiverecessive”” describes a trait that describes a trait that is covered over (or dominated) by another is covered over (or dominated) by another form of that trait and seems to disappear.form of that trait and seems to disappear.

• Homozygous= two alleles that are the Homozygous= two alleles that are the same for a trait (Pure)same for a trait (Pure)

• Heterozygous= two different alleles for a Heterozygous= two different alleles for a trait (Hybrid)trait (Hybrid)

PracticePractice• We use two letters to represent the genotype. A We use two letters to represent the genotype. A

capital letter represents the dominant form of a capital letter represents the dominant form of a gene (allele) and a lowercase letter is the gene (allele) and a lowercase letter is the abbreviation for the recessive form of the gene abbreviation for the recessive form of the gene (allele). (allele).

• Example below: P=dominant purple and p= Example below: P=dominant purple and p= recessive whiterecessive white

The phenotype for this flower is violet while its genotype (if homozygous) is PP.

The phenotype for this flower is white while its genotype is pp (to be white the flower must have two of the recessive copies of the allele).

Punnett SquaresPunnett Squares The Punnett square The Punnett square

is the standard way is the standard way of working out what of working out what the possible offspring the possible offspring of two parents will of two parents will be. be. – It is a helpful tool to It is a helpful tool to

show allelic show allelic combinations and combinations and predict offspring predict offspring ratios. ratios.

Before we go further lets review how Before we go further lets review how to set up a Punnett Square…to set up a Punnett Square…

We begin by constructing a grid of two We begin by constructing a grid of two perpendicular lines.perpendicular lines.

Next, put the genotype of one parent across Next, put the genotype of one parent across the top and the other along the left side.the top and the other along the left side.

For this example lets consider a genotype of BB crossed with bb.For this example lets consider a genotype of BB crossed with bb.

B Bb

b

• Notice only one letter goes above each box• It does not matter which parent’s genotype goes on either side.

Next, fill in the boxes by copying the Next, fill in the boxes by copying the column and row head-letters column and row head-letters downdown and and acrossacross into into

the empty spaces. the empty spaces.

B B

b B

B

B

Bb

b

b

b

b

Punnett SquaresPunnett Squares

Now that we have learned the Now that we have learned the basics of genetics lets walk basics of genetics lets walk through some examples using through some examples using Punnett Squares.Punnett Squares.

Lets say:W- dominant white w- recessive violet

W wW

Parents in this cross are heterozygous (Ww). Note: Make sure I can tell your capital letters from lowercase letters. What percentage of the offspring will have violet flowers? ANSWER: 25% (homozygous recessive)

Usually write the capital letter first

w

W W W w

W w w w

Red hair (R) is dominant over blond hair (r). Make a Red hair (R) is dominant over blond hair (r). Make a cross between a heterozygous red head and a cross between a heterozygous red head and a blond.blond.

RrRr rr rr

RrRr rr rr

R rr

r

What percentage of the offspring will have red hair? 50%

LetLet’’s try some more…s try some more…In pea plants, tall pea plants (T) are dominant In pea plants, tall pea plants (T) are dominant over short pea plants (t). Construct a Punnett over short pea plants (t). Construct a Punnett Square for a heterozygous tall pea plant and Square for a heterozygous tall pea plant and

a short pea plant.a short pea plant.

Tt tt

Tt tt

T ttt

What are the percentage of phenotypes?50% tall 50% short

Black eyes (R) is dominant over red eyes Black eyes (R) is dominant over red eyes (r) (r)

in rats. Make a cross between a in rats. Make a cross between a homozygous rat with black eyes and a homozygous rat with black eyes and a rat with red eyes. rat with red eyes.

Rr Rr

Rr Rr

R Rrr

What is the possibility of a red eye off springs?0%

ReferencesReferences http://www.athro.com/evo/gen/punnett.html http://www.kidshealth.org/kid/talk/qa/what_is_gene.html http://brookings.k12.sd.us/biology/ch%2011%20genetics/http://brookings.k12.sd.us/biology/ch%2011%20genetics/

punnettpractice.ppt#1punnettpractice.ppt#1 http://www.usoe.k12.ut.us/CURR/Science/sciber00/7th/gene

tics/sciber/punnett.htm http://www.biotechnologyonline.gov.au/images/http://www.biotechnologyonline.gov.au/images/

contentpages/karyotype.jpgcontentpages/karyotype.jpg

Bell Ringer 12/3/13Bell Ringer 12/3/13Add these terms to your vocab Add these terms to your vocab

chart:chart: HybridHybrid AlleleAllele DominantDominant RecessiveRecessive PhenotypePhenotype genotypegenotype

HomozygousHomozygous HeterozygousHeterozygous Law of Law of

segregationsegregation Law of Law of

Independent Independent AssortmentAssortment

These terms will be checked on Thursday during the bell ringer

http://http://images.search.yahoo.com/images.search.yahoo.com/

search/images?search/images?_adv_prop=image&fr=ytff1-_adv_prop=image&fr=ytff1-

yff24&va=heterochromia+iridyff24&va=heterochromia+iridumum

Heterochromia Heterochromia IridumIridum

Work with your group to Work with your group to complete the complete the

“punnett square practice” “punnett square practice” worksheetworksheet

Complete your punnett Complete your punnett square practice handout pg 2-square practice handout pg 2-

3 3 20 min20 min

Bell Ringer 12/3/13Bell Ringer 12/3/13

Self-grade your paperSelf-grade your paper For each of the genotypes (AA, Aa or

aa) below determine what the phenotype would be.

Purple flowers are dominant to white flowers.

PP - purple Pp - purple pp - white

AA – homoz dominantAA – homoz dominant GG – homoz dominantGG – homoz dominant TT – homoz dominantTT – homoz dominant Ff – heterozygousFf – heterozygous Pp – heterozygousPp – heterozygous Tt - hterozygousTt - hterozygous

Aa – heterozygousAa – heterozygous Ii – heterozygousIi – heterozygous aa – homoz recessiveaa – homoz recessive gg – homoz recessivegg – homoz recessive tt – homoz recessivett – homoz recessive Oo - heterozygousOo - heterozygous

Hairy knuckles are dominant to non-hairy knuckles in humans.

HH - hairy Hh - hairyhh - non-hairy Bobtails in cats are recessive.

Normal tails are dominant.TT - bobtail Tt - bobtail tt –

normal tail

Round seeds are dominant to wrinkled seeds in pea plants.

RR - round Rr - round rr – wrinkled

No-cleft chin is dominant. Cleft chin is recessive.CC – no cleft Cc – no cleft cc -cleft

2) For each of the following write whether it is

homozygous dominant, heterozygous or

homozygous recessive.

Use the following information for questions 3-5:

In dogs, the gene for fur color has two alleles. The dominant allele (F) codes for grey fur and the recessive allele (f) codes for black fur.

3) The female dog is heterozygous. The male dog is homozygous recessive. Figure out the phenotypes and genotypes of their possible puppies by using a Punnett Square.

4. The female dog has black fur. The male dog has black fur. Figure out the phenotypes and genotypes of their possible puppies by using a Punnett Square.

5) The female dog is heterozygous. The male dog is heterozygous. Figure out the phenotypes and genotypes of their possible puppies by using a Punnett Square.

Use the following information for questions 6-8:

In fruit flies, red eyes are dominant (E). White eyes are recessive (e).

 6) If the female fly has white eyes and the male fly has homozygous dominant red eyes, what are the possible phenotypes and genotypes of their offspring?

7) If the female fly has EE and the male fly has EE, what are the possible phenotypes and genotypes of their offspring?

8) If both flies are heterozygous, then what are the possible phenotypes and genotypes of their offspring?

Use the following for questions 9-11:

In dogs, there is an hereditary deafness caused by a recessive gene, “d.” A kennel owner has a male dog (Gilbert) that she wants to use for breeding purposes if possible. The dog can hear.

9) What are the two possible genotypes of Gilbert?– DD or Dd

10) If the dog’s genotype is Dd, the owner does not wish to use him for breeding so that the deafness gene will not be passed on. This can be tested by breeding the dog to a deaf female (dd). Draw two Punnett squares to illustrate these two possible crosses.

11) In each case, what percentage/how many of the offspring would be expected to be hearing? deaf? How could you tell the genotype of this male dog? Also, using Punnett square(s), show how two hearing dogs could produce deaf offspring.

Widow’s peak - dominantWidow’s peak - dominant No widow’s peak - recessiveNo widow’s peak - recessive

12) If Wentworth Miller is Aa, and he and Rihanna had children, what are the possible phenotypes and genotypes of their children?

13) Look at the phenotypes of Beyonce and Jay Z. If these two had children,

could they have children with a widow’s peak?

Why or why not?

Dihybrid Cross Dihybrid Cross Can you create a punnett square to Can you create a punnett square to

cross these two pea plants:cross these two pea plants:

TtRr x ttRrTtRr x ttRr*T=tall, t=short, R=round, r=wrinkled *T=tall, t=short, R=round, r=wrinkled

Hint: the punnett square is bigger than 4 Hint: the punnett square is bigger than 4 partsparts

Vocab chart checked Vocab chart checked tomorrowtomorrow

Punnett square quiz Punnett square quiz FridayFriday

Bell Ringer 12/5/13Bell Ringer 12/5/13 In humans, brown eyes (B) are

dominant over blue (b)*. A brown-eyed man marries a blue-eyed woman and they have three children, two of whom are brown-eyed and one of whom is blue-eyed. Draw the Punnett square that illustrates this marriage. What is the man’s genotype? What are the genotypes of the children?

Incomplete DominanceIncomplete Dominance In this case, neither allele is In this case, neither allele is

completely dominant over the other, completely dominant over the other, so the outcome of a cross is a 3so the outcome of a cross is a 3rdrd phenotype that is different from phenotype that is different from either of the ones that were crossedeither of the ones that were crossed

Example of incomplete Example of incomplete dominancedominance

When curly hair is crossed with straight hair, When curly hair is crossed with straight hair, sometimes wavy (a blend of the two) is the sometimes wavy (a blend of the two) is the outcome:outcome:

CC is curly (homozygous curly)CC is curly (homozygous curly)cc is straight (homozygous straight)cc is straight (homozygous straight)Cc is wavy (heterozygous)Cc is wavy (heterozygous)

What is the outcome of a cross between a What is the outcome of a cross between a curly haired father and a wavy haired mother?curly haired father and a wavy haired mother?

C CC

cCC

CCCc Cc

50% CC – curly50% CC – curly50% Cc – wavy50% Cc – wavy0% cc - straight0% cc - straight

Bell Ringer 12/9/13Bell Ringer 12/9/13 Read page 264 in the blue book, 269 Read page 264 in the blue book, 269

green bk. What is the difference green bk. What is the difference between a haploid cell and a diploid cell?between a haploid cell and a diploid cell?

Read the 1Read the 1stst paragraph under the paragraph under the subtitle “homologous chromosomes” on subtitle “homologous chromosomes” on page 265 blue or 270 green bk. What is page 265 blue or 270 green bk. What is a homologous chromosome?a homologous chromosome?

Complete Problem-solving lab 10.2 pg Complete Problem-solving lab 10.2 pg 265 or 270 green bk. 265 or 270 green bk.

MeiosisMeiosisMitosis MeiosisCell process beginning with a single cell (2n)

Cell process beginning with a single cell (2n)

Creates 2 body cells (daughter cells)

Creates 4 sex cells (gametes)

Results in 2 daughter cells Results in 4 gametes

Daughter cells are diploid (2n) Daughter cells are haploid (n)

On a clean sheet of paper:On a clean sheet of paper: Sketch and label the stages of Sketch and label the stages of

meiosismeiosis On your diagram write a summary On your diagram write a summary

sentence of what happens at each sentence of what happens at each stage.stage.

Complete this for homeworkComplete this for homework