17. Inheritance

Question 1

What are chromosomes made of?

Answer 1

DNA

Question 2

What does DNA contain?

Answer 2

genetic information in the form of genes

Question 3

What is a gene?

Answer 3

a length of DNA that codes for a protein

Question 4

Where is genetic information in the form of genes contained?

Answer 4

DNA

Question 5

A length of DNA that codes for a protein is…

Answer 5

a gene

Question 6

What is an allele?

Answer 6

an alternative form of a gene

Question 7

A girl would have ____ chromosomes.

Answer 7

XX

Question 8

An alternative form of a gene is…

Answer 8

an allele

Question 9

A boy would have _____ chromosomes.

Answer 9

XY

Question 10

What is a chromosome?

Answer 10

thread-like structure of coiled DNA

Question 11

What is DNA? What does it do?

Answer 11

• a large molecule made from bases
• carries genetic information in the form of genes

Question 12

Which gametes are contained in sperm cells?

Answer 12

X or Y

Question 13

Which gametes are contained in egg cells?

Answer 13

X

Question 14

What is the structure of DNA?

Answer 14

• two strands coil together to form double helix
• each strand contains bases (chemicals)

Question 15

What is a genetic code?

Answer 15

the sequence of bases in a gene

Question 16

What does the genetic code determine?

Answer 16

the sequence of amino acids used to make a specific protein

Question 17

What determines the sequence of amino acids used to make a specific protein?

Answer 17

the sequence of bases in a gene

Question 18

What does the sequence of bases in a gene determine?

Answer 18

the sequence of amino acids used to make a specific protein

Question 19

What gives different shapes to protein molecules?

Answer 19

different sequences of amino acids

Question 20

Different sequences of amino acids give…

Answer 20

different shapes to protein molecules

Question 21

What is the role of DNA?

Answer 21

controlling cell function by controlling the production of proteins

Question 22

What are some types of protein?

Answer 22

• enzymes
• membrane carriers
• antibodies
• receptors for neurotransmitters

Question 23

Explain how a protein is made.

Answer 23

1. a DNA molecule in the nucleus unzips, exposing the bases in a gene
2. mRNA molecule formed using the exposed bases of the DNA strand as a template
3. bases in mRNA molecule pair with complementary bases in the DNA, so the mRNA molecule now carries a copy of the gene
4. mRNA molecule moves out of the nucleus into the cytoplasm
5. ribosome reads the mRNA code
6. ribosome joins amino acids together to form a protein, following the specific sequence of bases in the mRNA

Question 24

Why are many genes in a particular cell not expressed?

Answer 24

because the cell only makes the specific proteins it needs

Question 25

What do most body cells in an organism contain?

Answer 25

the same genes

Question 26

The same genes are contained in...

Answer 26

most body cells

Question 27

A cell only makes the specific proteins it needs. Therefore...

Answer 27

many genes in a particular cell are not expressed

Question 28

What is a haploid nucleus?

Answer 28

a nucleus containing a single set of chromosomes

Question 29

What is a diploid nucleus?

Answer 29

a nucleus containing two sets of chromosomes

Question 30

In a diploid cell, there is a pair of each type of ______.

Answer 30

chromosome

Question 31

How many chromosomes are in a human diploid cell?

Answer 31

23 pairs, 46 chromosomes: a pair of each type of chromosome

Question 32

Define mitosis.

Answer 32

nuclear division giving rise to genetically identical cells

Question 33

What are some roles of mitosis?

Answer 33

- growth - repair of damaged tissues - replacement of cells - asexual reproduction

Question 34

What determines the sequence of amino acids in a protein?

Answer 34

the sequence of bases on an mRNA molecule

Question 35

What molecule carries genetic information from the nucleus to the cytoplasm?

Answer 35

mRNA

Question 36

What must happen before mitosis takes place?

Answer 36

the exact replication of chromosomes (so that there are two copies of each chromosome when the cell is about to divide)

Question 37

Outline the process of mitosis.

Answer 37

1. two copies of each chromosome are joined together near the middle 2. nucleus divides into two 3. one copy of each chromosome goes into each new cell 4. this keeps the number of chromosomes in the two daughter cells the same as in the original cell

Question 38

What happens during mitosis?

Answer 38

the copies of chromosomes separate, maintaining the chromosome number in each daughter cell

Question 39

Define stem cells.

Answer 39

unspecialised cells, divide by mitosis to produce daughter cells. these daughter cells can become specialised for specific functions

Question 40

What is the role of meiosis?

Answer 40

production of gametes

Question 41

Describe meiosis.

Answer 41

reduction division: the chromosome number is halved, resulting in genetically different cells

Question 42

Define inheritance.

Answer 42

the transmission of genetic information from generation to generation

Question 43

Define genotype.

Answer 43

the genetic make-up of an organism and in terms of the alleles present

Question 44

The genetic make-up of an organism and in terms of the alleles present is...

Answer 44

the genotype

Question 45

The transmission of genetic information from generation to generation is...

Answer 45

inheritance

Question 46

Define phenotype.

Answer 46

the observable features of an organism

Question 47

The observable features of an organism is...

Answer 47

phenotype

Question 48

What does the term homozygous mean?

Answer 48

having two identical alleles of a particular gene

Question 49

What causes pure breeding?

Answer 49

two identical homozygous individuals that breed together

Question 50

What does the term heterozygous mean?

Answer 50

having two different alleles of a particular gene

Question 51

Which type of individual will not be pure-breeding?

Answer 51

heterozygous

Question 52

Heterozygous individuals will NOT be...

Answer 52

pure-breeding

Question 53

What is a dominant allele?

Answer 53

an allele that is always expressed if it is present in the genotype

Question 54

What is a recessive allele?

Answer 54

an allele that is only expressed when there is no dominant allele present in the genotype

Question 55

What is a test cross?

Answer 55

a cross with a homozygous recessive individual

Question 56

What is a test cross used for?

Answer 56

to determine the genotype of an individual showing the dominant trait, to find out whether it has DD or Dd

Question 57

What is codominance?

Answer 57

a situation in which both alleles in heterozygous organisms contribute to the phenotype

Question 58

What is a sex-linked characteristic?

Answer 58

- feature in which the gene responsible is located on a sex chromosome - makes the characteristic more common in one sex than in the other

Question 59

What is a an example of sex linkage?

Answer 59

red-green colour blindness