nucleotides

B
-
4 Demonstrate an
understanding of the molecular
basis of heredity

Genetics Review

B 4.1 Compare DNA and RNA in
terms of structure, nucleotides,
and base pairs.

Nucleic Acids

•
Nucleic acids are made of
nucleotides
.

•
Nucleotides have three parts:

–
Sugar

–
Phosphate

–
Base

RNA vs. DNA

Sugar:


Ribose


Bases:


A, U, C, G


Shape:

single strand of
nucleotides

Sugar:


Deoxyribose


Bases:


A,
T,
C, G


Shape:

Double helix

DNA vs. RNA

I am:



double
stranded



found
in the nucleus



have
four nitrogen bases



contain
deoxyribose

sugar



contain
thymine instead of uracil


1.
What important molecule am I
?


A. DNA


B. RNA


C. Enzyme


D.protein



B 4.2 Summarize the relationship
among DNA, genes, and
chromosomes.

DNA, Genes, and Chromosomes

DNA

•
made of nucleotides

•
blueprint for proteins


Genes

•
a segment of DNA

•
a specific location on a
chromosome

•
A code for a protein


Chromosome

•
One long thread of DNA
with many genes


DNA, Genes, and Chromosomes

A segment of DNA that codes for the ability to
make one type of protein molecule is known as
a(n)____________________
.

A.
Codon

B.
Exon

C.
Gene

D.
I
ntron


B 4.3 Explain how DNA functions as
the code of life and the blueprint
for proteins.

Blueprint for
Proteins

•
The sequence of bases in DNA determines which
protein is made

•
Each cell has a complete set of information
—
two
copies of each autosome and a pair of sex
chromosomes (46 total chromosomes in humans)

•
Sex cells have one set of chromosomes (23 in
humans)

•
Organisms that are closely related will have many
genes in common.

How DNA becomes a Protein

DNA
Replication

Semi
-
Conservative Model of Replication

Blueprint for Proteins

The process of converting the genetic message
from DNA into __________ is called
transcription
.

A.
RNA

B.
amino
acid

C.
nucleic
acid

D.
nucleotide base


B 4.4 Summarize the basic
processes involved in protein
synthesis (including transcription
and translation).

Protein Synthesis

Transcription:

•
DNA is copied into RNA

•
Happens in the nucleus

•
Messenger RNA moves to
the cytoplasm


Translation:

•
Ribosomal RNA reads a code off
of the mRNA

•
Each codon is 3 nucleotides

•
Transfer RNA has a matching
anticodon and drops off amino
acids at the correct location

Which
type of nucleic acid is responsible for the
transmission of information from the genetic
code in the nucleus to the ribosome
?

A.
DNA

B.
mRNA

C.
rRNA

D.
tRNA



What type of biomolecule will be produced at
the end of the process shown in the illustration
?

A.
a
fat

B.
a
sugar

C.
a
lipid

D.
a protein


B 4.5 Summarize the
characteristics of the phases of
meiosis I and II.

Prophase I

Form a cluster of four
chromatids called a tetrad

Two haploid cells

Four haploid cells

Meiosis vs. Mitosis

Meiosis

In normal humans, sex cells contain the
_________ number of chromosomes
.

A.
Diploid

B.
Haploid

C.
Multiploid

D.
Tetraploid



In order for meiosis to create four, genetically
different gametes, DNA replication must occur.
Which of these best describes when DNA
replication would occur during meiosis
?

A.
interphase of meiosis
I

B.
anaphase I in meiosis
I

C.
interphase in meiosis
II

D.
anaphase II in meiosis II


B 4.6 Predict inherited traits by
using the principles of
Mendelian

genetics (including segregation,
independent assortment, and
dominance)

Inheritance of Traits
-

Dominance

Some alleles are
dominant and some are
recessive.


Having two identical
alleles for the same trait
(TT or
tt
) is homozygous


Having two different
alleles for the same trait
(
Tt
) is heterozygous

Genotype vs. Phenotype

•
Genotype
: the genetic makeup

–
Example: TT is homozygous dominant





Tt

is heterozygous





tt

is homozygous recessive

•
Phenotype
: the physical characteristics or
expression of a trait

–
Example: tall or short

Law of Segregation

Each parent has two
copies of each gene.


Each gamete gets only
one of the two copies.


When egg and sperm
fuse (fertilization), the
child receives one copy
from each parent.

Law of Independent
Assortment

•
The segregation of the
alleles of one trait does not
affect the alleles of another
trait’s alleles.


•
Genes on separate
chromosomes can separate
independently.

•
Exception: “linked genes”
are found on the same
chromosome
—
they are
sometimes inherited
together

Mendelian

Genetics

In
a classic experiment using pea shape, Mendel conducted two
separate genetic crosses. In the first cross the parent plants were “true
breeding
” for pea shape; one had round peas ( R )and the other had
wrinkled (r). The first cross produced a filial 1 generation of all round
peas. In the second cross, Mendel bred plants from the filial 1
generation. This cross produced different results. Out of approximately
1000 plants, about 75% were round and 25% were wrinkled.


From these experiments, Mendel developed four hypotheses. They
include all
BUT

A.
one heritable factor may be dominant and mask the other factor.

B.
any organism that "shows" a heritable factor must be
homozygous.

C.
an organism has two "heritable factors", now called genes, one
from each parent.

D.
a sperm or egg carries only one heritable factor for each trait in
the offspring.


Mendelian

Genetics

A dominant gene that codes for red eye color in
fruit flies is represented by the symbol W, while the
recessive white eye gene is represented by the
symbol w. If a parent fly with the genotype WW is
crossed with a parent of the genotype
Ww
, what
percentage the offspring will have red eyes
?

A.
100
%

B.
75
%

C.
50
%

D.
25%


B 4.7 Summarize the chromosome
theory of inheritance.

Codominance

vs. Incomplete
Dominance

Incomplete Dominance
:
Blending of alleles in
heterozygous individuals


Example: pink flowers

Codominance

Heterozygous
individuals express
both dominant traits

Polygenic Traits

Two or more genes affect the phenotype
of one trait

Sex
-
linked Traits

Pedigree Charts

Constructed to show the inheritance of a trait within a family

Complex Inheritance

A cross between a blue
blahblah

bird & a white
blahblah

bird produces offspring that are silver.


The
color of
blahblah

birds is determined by just two alleles.

1.
What
are the genotypes of the parent
blahblah

birds in the original cross
? (choose 1 or 2)



A. BB



B. Bb


C. BW


D. WW

2.
What
is/are the genotype(s) of the silver
offspring



A. BB



B
. Bb


C. BW


D
.
WW

3.
What
would be the phenotypic ratios of offspring
produced by two silver
blahblah

birds
?



A. 1:2:1


B. 3:1


C. 4:0



D. 1:1

B 4.8 Compare the consequences
of mutations in body cells with
those in gametes.

Mutations

•
Can affect somatic cells or sex cells:

–
Mutations in somatic cells with affect other
daughter cells, but NOT future offspring.

–
Mutations in gametes can be passed on to the
offspring AND all future generations.

•
DNA changes can be:

–
Gene mutations: affecting only a single gene

–
Chromosomal mutations: affecting a group of
genes or a whole chromosome

Gene Mutations

Occur during replication

Chromosome Mutations

Occur during cell division

Mutations

Transcription translation errors often result in
physical, or ___________, changes in an
organism
.

A.
Carbohydrate

B.
Chemical

C.
Genotypic

D.
Phenotypic


B 4.9 Exemplify ways that
introduce new genetic
characteristics into an organism or
a population by applying the
principles of modern genetics.

Genetic Engineering

•
Genetic engineering: the process of replacing
specific genes in an organism in order to
ensure expression of a desired trait

–
Gene map: Shows where genes are on a
chromosome

–
Cloning: creating a copy of a gene or organism

–
Gene therapy: inserting a normal gene to replace
a missing or abnormal gene

Selective Breeding

•
Selective Breeding is only breeding those
organisms with desired traits

–
Examples: crops and most domestic animals

–
Inbreeding: crossing closely related individuals

•
Hybridization: selective breeding in order to
create a combination of desired traits

–
Example: a mule
—
stronger than a horse but more
intelligent and less stubborn than a donkey

DNA Fingerprinting

•
DNA is copied and
chopped into
fragments

•
Fragments are sorted
by length

•
A matching set of
samples means the
samples came from
the same organism

Genetic Engineering

________ is a technique that involves putting a
healthy copy of a gene into cells that have a
defective copy of the same gene
.

A.
Gene
therapy

B.
Binary
fission

C.
Tumor
necrosis

D.
DNA fingerprinting