1

Modern Genetics

Chapter 4

2

Human Inheritance

Some human traits are controlled by single genes with two alleles, and others by single genes with multiple alleles. Still other traits are controlled by many genes that act together.

3

The Sex Chromosomes

Sex chromosomes are one of 23 pairs of chromosomes in each body.

The sex chromosomes carry genes that determine whether a person is male or female.

They also carry genes that determine other traits.

4

Sex-Linked Genes

Genes on the X and Y chromosomes are often called sex-linked genes.

A carrier is a person who has one recessive allele for a trait and one dominant allele.

5

Sex-Linked Traits

Colorblindness Male patterned

baldness. Hemophilia. Duchene Muscular

Dystrophy.

6

Environment

Many of a person’s characteristics are determined by an interaction between genes and the environment.

7

Human Genetic Disorders

A genetic disorder is an abnormal condition that a person inherits through genes or chromosomes. Cystic Fibrosis Sickle-Cell Disease Hemophilia Down Syndrome

8

Genetic Disorders

Some genetic disorders are caused by mutations in the DNA of genes.

Other disorders are caused by changes in the overall structure or number of chromosomes.

9

Pedigrees

A pedigree is a chart of “family tree” that tracks which members of a family have a particular trait.

10

Managing Genetic Disorders

Karyotype is a picture of all the chromosomes in a cell.

Genetic counseling helps couples understand their chances of having a child with a particular genetic disorder.

11

Dealing with Genetic Disorders

Medical Care. Education. Job Training.

12

Advances in Genetics

Selective breeding. Cloning. Genetic engineering.

13

Selective Breeding

Inbreeding involves crossing two individuals that have similar characteristics.

Hybridization is the cross between two genetically different individuals.

14

Cloning

A clone is an organism that has exactly the same genes as the organism for which it was produced.

15

Genetic Engineering

Genetic engineering is when genes from one organism are transferred into the DNA of another organism. Bacteria. Cows. Gene therapy. Genetically altered crops.

16

Education About Genetics

A genome is all the DNA in one cell of an organism.

The main goal of the Human Genome Project has been to identify the DNA sequence of every gene in the human genome.

Paramecia usually reproduce asexually. Fish reproduce sexually. Suppose the environmental conditions in the lagoon change. What advantage will the fish population have over the paramecium population?

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1. Se

xual r

eproducti

on...

2. Se

xual r

eproducti

on...

3. Se

xual r

eproducti

on ...

4. Se

xual r

eproducti

on ...

0% 0%0%0%

1. Sexual reproduction produces offspring that are identical to the parents.

2. Sexual reproduction decreases the genetic variability in the fish populations.

3. Sexual reproduction limits the spread of harmful characteristics in fish populations.

4. Sexual reproduction allows populations to adapt to new conditions over fewer generations. :10

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What is one advantage of sexual reproduction?

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does not r

equi...

allows f

or div...

does not a

llow...

does not r

equi...

0% 0%0%0%

:10

1. does not require a lot of calories

2. allows for diversity

3. does not allow for diversity

4. does not require two organisms

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What is one advantage of asexual reproduction?

19

require

s a lo

t...

allows f

or div...

does not a

llow...

require

s two d...

0% 0%0%0%

1. requires a lot of calories

2. allows for diversity

3. does not allow for diversity

4. requires two different organisms

:10

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Which of the following is not an example of asexual reproduction?

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Budding

dispersa

l of s

...

fission

mating

0% 0%0%0%

1. Budding

2. dispersal of spores

3. fission

4. mating

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How has sexual reproduction enhanced a species’ chance for survival?

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Sexual re

produ...

Sexual re

produ...

Sexual re

produ...

Sexual re

produ...

0% 0%0%0%

1. Sexual reproduction produces offspring with unique traits.

2. Sexual reproduction always produces offspring that are identical.

3. Sexual reproduction does not allow for genetic variation.

4. Sexual reproduction between two different species produces offspring that can not reproduce.

:10

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From whom does an offspring get its traits?

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Mom

Dad

both a

and b

neither a

nor ...

0% 0%0%0%

1. Mom

2. Dad

3. both a and b

4. neither a nor b

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Which of the following terms describe the appearance of the organism?

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Allele

Genotyp

e

homozygous

phenotype

hetero

zygous

0% 0% 0%0%0%

1. Allele

2. Genotype

3. homozygous

4. phenotype

5. heterozygous :10

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Which term describes a trait that is always expressed when present?

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dominant

genoty

pe

phenotype

rece

ssive

0% 0%0%0%

1. dominant

2. genotype

3. phenotype

4. recessive

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Which term describes two of the same allele?

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dominant

hetero

zygous

homozygous

rece

ssive

0% 0%0%0%

1. dominant

2. heterozygous

3. homozygous

4. recessive :10

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Given the genotype Bb, B is dominant for brown eyes and b is recessive for blue eye, what is the genotype and phenotype?

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Hetero

zygo

us b...

Hetero

zygo

us b...

Homozy

gous b

lu...

Homozy

gous b

ro...

0% 0%0%0%

1. Heterozygous blue eyes

2. Heterozygous brown eyes

3. Homozygous blue eyes

4. Homozygous brown eyes

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Two adults decide to have a baby. If one parent has brown eyes (BB), which is a dominant trait and the other parent has blue eyes (bb), which is a recessive trait, what is the probability that they will have a baby with blue eyes?

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100%75%

50%25% 0%

0% 0% 0%0%0%

1. 100%

2. 75%

3. 50%

4. 25%

5. 0%

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A red four o’clock flower was crossed with a white four o’clock flower. With Incomplete dominance as a factor, what is the phenotype of the offspring?

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100% red

100% white

50% red, 5

0% w...

100% pink

0% 0%0%0%

1. 100% red

2. 100% white

3. 50% red, 50% white

4. 100% pink

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What is the phenotype of the F1 generation from the Punnett square?

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100% tall

100% short

50 % ta

ll, 50%...

75 % ta

ll, 25%...

0% 0%0%0%

1. 100% tall

2. 100% short

3. 50 % tall, 50% short

4. 75 % tall, 25% shortT T

T

t

:10

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