Download (b).

The DNA sequence of the nitrogen bases (A, T, G, C) contains the gene:c code that determines an organism’s traits. Review: DNA Chromosomes & Genes Homologous chromosomes are the same size and shape and carry informa:on to make the same proteins and determine the same traits. Humans have 23 pairs of homologous chromosomes (23 from mom and 23 from dad). Insert the homologous pair cutouts into your notebook § An organism produces gametes (sex
cells) to maintain the same number of
chromosomes from generation to
generation.
§ Human gametes contain 23
chromosomes each.
§ A cell with one set of chromosomes is
called a haploid cell. (n)
§ A cell with two sets of chromosomes is
called a diploid cell. (2n)
§ Meiosis
produces
gametes.
§ When
gametes unite
during
fertilization,
the number of
chromosomes
is restored.
N + N  2N
Review:
Sexual vs. Asexual
§ Asexual reproduction
§ One parent
§ The new individual is genetically
identical to its parent.
§ Sexual reproduction
§ Two parents
§ Beneficial genes multiply faster over time.
§ Genetic variation
How the Study of Genetics Began
The passing of traits to the next
generation is called inheritance, or
heredity.
§ Gregor Mendel performed cross-pollination
in pea plants.
§ Mendel followed various traits in the pea
plants he bred.
§ Cross pollination in pea plants
§ https://vimeo.com/49408412
Gregor Mendel: 100 Greatest Discoveries
Mendelian Genetics
Review Scien:fic Method: Independent Variable Dependent Variable Constants Mendelian Genetics
Genes in Pairs
§ Allele
§ An alternative form of a single gene
passed from generation to generation
§ We use letters of the alphabet to
represent alleles
§ Dominant (uppercase letter)
§ Recessive (lowercase letter)
Mendelian Genetics
Dominance
§ An organism with two of the same alleles
for a particular trait is homozygous.
§ Both alleles (letters) are either dominant or
recessive.
§ Homozygous dominant: AA, RR, TT, etc.
§ Homozygous recessive: aa, rr, tt, etc.
Mendelian Gene9cs different alleles
§ An organism with two
for a particular trait is heterozygous.
One allele is dominant, and one allele
is recessive.
§ Aa, Ee, Tt, etc.
§ An organism with heterozygous
alleles would express the dominant
form of the trait. (the uppercase letter
DOMINANTS over the lowercase
letter)
Mendelian Genetics
Genotype and Phenotype
§ An organism’s allele pairs are
called its genotype.
§ The genotype is the pair of letters
§ AA, Aa, aa
§ The observable characteristic or
outward expression of an allele
pair is called the phenotype.
Make a Bunny!
and
Bioethics in Genetic
Testing!
Which symbol is used to represent the
number of chromosomes in a gamete?
A.  #
B.  x
C.  r
D.  n
Which person is known as the
father of genetics?
A.  Felix Mendelssohn
B.  Gregor Mendel
C.  Bill Nye
D.  Albert Einstein
Which term refers to the outward
physical expression of an allele pair?
A.  gamete
B.  hybrid
C.  phenotype
D.  genotype
What are the segments of DNA that
control the production of proteins?
A.  chromatids
B.  chromosomes
C.  genes
D.  traits
What type of organisms can only
reproduce asexually?
A.  bacteria (prokaryote)
B.  protists (unicellular eukaryote)
C.  plants (eukaryote)
D.  animals (eukaryote)
What is the name for different forms of a
single gene that are passed from generation to
generation?
A.  alleles
B.  genotypes
C.  phenotypes
D.  traits
Which pair of alleles is heterozygous?
A. RR
B. Rr
C. rr
D. yR
Homozygous Dominant Heterozygous Homozygous Recessive What is this process called?
A.  fertilization
B.  gamete formation
C.  inheritance
D.  reproduction
Monohybrid Cross
The monohybrid
cross was
invented by Gregor
Mendel.
In a monohybrid
cross, organisms
differing in only
one trait are
crossed.
http://youtu.be/
MWkFxWXHTnw
What is a PUNNETT SQUARE?
•  A tool to predict the probability of certain traits
in offspring
•  It shows the different ways alleles can combine
•  Genotypes use letters to represent dominant and
recessive alleles
•  An uppercase letter stands for a dominant allele
•  Lowercase letters stand for recessive alleles
Using a PUNNETT SQUARE
To set up a Punnett square, draw a large
square, and then divide it into 4 equal
sections.
Using a PUNNETT SQUARE
In order to predict the probability a
trait, you must know the genotype of
each parent.
For example, a red flower (genotype Rr)
and a white flower (genotype rr).
Rr x rr
Using a PUNNETT SQUARE
Place one parent’s genotype on top, and
one on the left. Using a PUNNETT SQUARE
Then, take each allele in each column and
combine it with each allele from each row
in the corresponding square. Using a PUNNETT SQUARE
The possible genotype combinations of the
offspring are:
Rr, Rr, rr, and rr
We now know that the probability of the
offspring having a red phenotype is 2/4 or
50% or a white phenotype 2/4 or 50%.
G g G GG Gg
g Gg gg
The parents in this cross Heterozygous are _____________ Homozygous OR Heterozygous If G is dominant for green pods and g is recessive for yellow pods, what percentage of the offspring will have green pods? _______% 75 B b
B
b
The genotype of the offspring in the red box is bb _______ The offspring in the red box is: homozygous OR heterozygous homozygous recessive In guinea pigs, black fur (B) is dominant over brown fur (b). Which of the following PunneP squares would represent a cross between a HETEROZYGOUS black guinea pig and a PURE brown guinea pig? B B
B b
B b
B b
B
b
b
B
b
b
b
B
This is the correct setup! Heterozygous = Bb Pure brown = bb homozygous Another name for pure is _____________ R r r r Rr rr Rr rr Red throats (R) are dominant over white (r) throats in Goonie birds. Make a cross between a PURE RECESSIVE and a HETEROZYGOUS Goonie bird. What are the possible phenotypes of their offspring? (% and color) 50% red throats 50% white throats PICTURE B b B b B B Bb Bb bb Black eyes (B) are dominant over red eyes (b) in rats. Make a cross between two HETEROZYGOUS rats. What are the possible phenotypes of their offspring? (% and color) 75 % black eyes 25% red eyes The parents in this cross homozygous are _____________ Homozygous OR Heterozygous If W is dominant for long wings and w is recessive for short wings, what percentage of these offspring will have short wings? 0% only ww has the phenotype short wings Which of the following genotypes could be from a HETEROZYGOUS organism? TT Rr Ww bb XX Ss Rr Ww Ss What kind of cross is this? Pure Dominant X Pure Recessive OR Heterozygous X Heterozygous OR Heterozygous X Homozygous OR Hybrid Recessive X Hybrid Pure Heterozygous X Homozygous hybrid Another name for heterozygous is _______________ T T t Tt Tt t Tt Tt In pigs, curly tails (T) are dominant over straight tails (t). Make a cross between a HOMOZYGOUS DOMINANT and a HOMOZYGOUS RECESSIVE pig. What is the probability the offspring will have straight tails? 0% All will be curly tailed (Tt) Which of the following genotypes could be from a HOMOZYGOUS RECESSIVE organism? TT bb Rr Ww P XX aa bb P aa A a
A
a
The genotype of the offspring in the red box is heterozygous ________________ homozygous OR heterozygous How many of the offspring from this cross will show the dominant characteris9c? ¾ (75%) G g
G
g
GG Gg
G is dominant for green pods. g is recessive for yellow pods. What is the genotype of the offspring in the blue box? gg
Gg What is the phenotype of the offspring in the blue box? Green pods r r R R Pp Pp Pp Pp Purple (R) is the dominant color for monsters. Yellow is recessive (r). Make a cross between a HOMOZYGOUS purple and a yellow monster. What will the offspring be like? (% and color) 100% purple What genotype would a PURPLE dad have to be to make a yellow monster baby with a purple (Pp) mom monster? P
?
?
p
Baby is pp Dad is Pp Dad needs to have: a liPle p to give one to the baby a big P to be purple himself Which of the following is NOT TRUE? T Genotype determines phenotype T Alleles are different forms of the same gene. F Genotype is what an organism looks like. T Organisms with different genotypes c
an h
ave t
he s
ame p
henotype. Gene:cs Using Punnea Squares Early Gene:cs •  The study of gene:cs began with observa:ons made by Gregor Mendel. •  Acer no:cing that the flowers his pea plants were either violet or white, Between 1856 and 1863 he Mendel began to study the cul:vated and tested at least 28,000 pea plants. segrega:on of heritable traits. Remember that Mendel worked almost 150 years ago when nobody knew about genes or even the structures (chromosomes) that carry genes. Lets consider a single gene… •  A gene carries informa:on that determines your traits. Traits are characteris:cs you inherit from your parents. •  Genes are located in chromosomes. •  Chromosomes come in pairs and there are thousands, of genes in one chromosome. Defini:ons •  Allele-­‐ discrete version of the same gene •  Genotype-­‐ the genes of an organism for one specific trait •  Phenotype-­‐ the physical appearance of a trait in an organism Defini:ons •  Dominant trait refers to a gene:c feature that “hides” the recessive trait in the phenotype of an individual. •  The term "recessive” describes a trait that is covered over (or dominated) by another form of that trait and seems to disappear. •  Homozygous= two alleles that are the same for a trait (Pure) •  Heterozygous= two different alleles for a trait (Hybrid) Prac:ce •  We use two leaers to represent the genotype. A capital leaer represents the dominant form of a gene (allele) and a lowercase leaer is the abbrevia:on for the recessive form of the gene (allele). •  Example below: P=dominant purple and p= recessive 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). Punnea Squares •  The Punnea square is the standard way of working out what the possible offspring of two parents will be. –  It is a helpful tool to show allelic combina:ons and predict offspring ra:os. Before we go further lets review how to set up a Punnea Square… We begin by construc:ng a grid of two perpendicular lines. Next, put the genotype of one parent across the top and the other along the lec side. For this example lets consider a genotype of BB crossed with bb. •  No:ce only one leaer goes above each box B B b b •  It does not maaer which parent’s genotype goes on either side. Next, fill in the boxes by copying the column and row head-­‐leaers down and across into the empty spaces. B B b B b B b b B b B b Punnea Squares •  Now that we have learned the basics of gene:cs lets walk through some examples using Punnea Squares. R r R R R R r r R r r r Usually write the capital leaer first Lets say: R -­‐ dominant white r -­‐ recessive violet Parents in this cross are heterozygous (Ww). Note: Make sure I can tell your capital leaers from lowercase leaers. What percentage of the offspring will have violet flowers? ANSWER: 25% (homozygous recessive) Red hair (R) is dominant over blond hair (r). Make a cross between a heterozygous red head and a blond. R r r r Rr
rr
Rr
rr
What percentage of the offspring will have red hair? 50% Let’s try some more… In pea plants, tall pea plants (T) are dominant over short pea plants (t). Construct a Punnea Square for a heterozygous tall pea plant and a short pea plant. What are the percentage of phenotypes? t T t Tt
tt
t Tt
tt
50% tall 50% short Black eyes (R) is dominant over red eyes (r) in rats. Make a cross between a homozygous rat with black eyes and a rat with red eyes. r R R Rr
Rr
r Rr
Rr
What is the possibility of a red eye off springs? 0% L Karyotypes Pedigrees Sex-­‐Linked Traits Muta:ons Gene:c Disorders The Human Genome Consists of 23 pairs of chromosomes. Images are taken from diploid cells during mitosis. •  Chromosomes 1 through 22 are called autosomes. •  The X and Y chromosomes are the sex chromosomes. –  Males are XY. –  Females are XX. Karyotyping 1 Karyotyping Explained A karyotype is an organized profile of an organism’s chromosomes. This arrangement helps scien:sts quickly iden:fy chromosomal altera:ons that may result in a gene:c disorder. To create a karyotype, scien:sts take a picture of the chromosomes from one cell, cut them out, and arrange them using size, banding paaern, and centromere posi:on as guides. This is karyotype from a human male. How do we know??? Karyotyping Can you iden:fy the chromosome abnormality in this karyotype? Is this individual a male or a female? Sex Determination
Sex chromosomes
determine an
individual’s gender.
In sex-­‐linked traits, the gene for the trait is found on the X chromosome, a sex chromosome, not an autosome. Sex-­‐linked traits affect primarily males, since they have only one copy of the X chromosome (male genotype: XY). Females, who have two copies of the X chromosome, are affected only if they are homozygous for the trait. Females can, however, be carriers for sex-­‐linked traits, passing their X chromosomes on to their sons. Another example of a sex-­‐linked trait is hemophilia, made famous by the "Queen Victoria pedigree" of the European nobility. Beginning with Queen Victoria of England (in whom it was probably a spontaneous muta:on), the hemophilia gene spread quickly throughout the European rulers (who intermarried). The disease, which prevents blood from clopng properly and renders a minor injury a life-­‐threatening event, claimed several in the royal line. Calico Cats #1 Black
Calico Cats #2 Black
Watch Paul Anderson’s hap://youtu.be/
Bozemon Biology Y9vXhmI5FXM Calico Cats MUTATIONS Changes in DNA that affect gene:c informa:on What Are
Mutations?
•  Changes in the nucleotide sequence of DNA
•  May occur in somatic cells (body cells)
–  are NOT passed to offspring
•  May occur in gametes (eggs & sperm)
–  are passed to offspring
Gene Muta:ons Remember – the ‘Central Dogma’ Nucleo:des à DNA à RNA à Amino Acid à Protein àTrait Note: The only way asexually reproducing organisms have gene:c varia:on is through a muta:on Muta:on in Soma:c Cells Muta:on in Gametes Chromosome Muta:ons •  Changes in number and structure of en:re chromosomes •  Original Chromosome ABC * DEF •  Dele:on AC * DEF •  Duplica:on ABBC * DEF •  Inversion AED * CBF •  Transloca:on ABC * JKL GHI * DEF Significance of Muta:ons • Most are neutral • Eye color • Birth marks • Some are harmful • Sickle Cell Anemia • Down Syndrome • Some are beneficial • Sickle Cell Anemia Immune to Malaria What Causes Muta:ons? •  There are two ways in which DNA can become mutated: – Muta9ons can be inherited. • Parent to child – Muta9ons can be acquired. • Environmental damage – Radia9on, chemicals, UV light, etc. Complex Inheritance and Human Heredity
Identify the disease characterized by the
absence of melanin.
A.  albinism
B.  cystic fibrosis
C.  galactosemia
D.  Tay-Sachs
Under what circumstances will a recessive
trait be expressed?
A.  A recessive allele is passed on by both
parents.
B.  One parent passes on the recessive allele.
C.  The individual is heterozygous for the trait.
D.  There is a mutation in the dominant
gene.
Which is the genotype of a person who is
a carrier for a recessive genetic disorder?
A.  DD
B.  Dd
C.  dd
D.  dE
Albinism is a recessive condition.
If an albino squirrel is born to parents that both
have normal fur color, what can you
conclude about the genotype of the parents?
A.  at least one parent is a carrier
B.  both parents are carriers
C.  both parents are homozygous recessive
D.  at least one parent is homozygous
dominant
Of the 23 pairs of chromosomes in human
cells, one pair is considered to be the ____________.
A.  autosomes
B.  Barr bodies
C.  monosomes
D.  sex chromosomes
What does a karyotype show?
A.  The blood type of an individual.
B.  The locations of nitrogen bases on a
chromosome.
C.  The cell’s chromosomes arranged in order.
D.  The phenotype of individuals in a pedigree.
If a genetic disorder is caused by a dominant
allele, what is the genotype of those who do
not have the disorder?
A.  heterozygous
B.  homozygous dominant
C.  homozygous recessive
Why are males affected by recessive sexlinked traits more often than are females?
A.  Males have only one X chromosome.
B.  Males have two X chromosomes.
C.  Males have only one Y chromosome.
D.  The traits are located on the Y
chromosomes.
Complete Gene9cs Prac9ce Problems 2 Worksheet!