Chapter 4

Question 1

structural genes

Answer 1

Genes that contain the informa­ tion to make a protein.

Question 2

regulatory genes

Answer 2

Genes that guide the expression of structural genes, without coding for a protein themselves.

Question 3

genotype

Answer 3

The genetic makeup of an individ­ ual. Genotype can refer to the entire genetic complement or more narrowly to the alleles present at a specific locus on two homologous chromosomes.

Question 4

phenotype

Answer 4

An observable or measurable fea­ ture of an organism. Phenotypes can be anatomical, biochemical, or behavioral.

Question 5

ABO blood type system

Answer 5

Refers to the genetic system for one of the proteins found on the surface of red blood cells. Consists of one gene with three alleles: A, B, and O.

Question 6

recessive

Answer 6

In a diploid organism, refers to an allele that must be present in two copies (homozygous) in order to be expressed.

Question 7

dominant

Answer 7

In a diploid organism, an allele that is expressed when present on only one of a pair of homologous chromosomes.

Question 8

codominant

Answer 8

In a diploid organism, two dif­ ferent alleles of a gene that are both expressed in a heterozygous individual.

Question 9

particulate inheritance

Answer 9

The concept of heredity based on the transmission of genes (alleles) according to Mendelian principles.

Question 10

Mendel’s law of segregation

Answer 10

Law of Segregation: This law states that during the formation of gametes (sperm and egg cells), the two alleles for a gene segregate (separate) from each other, and each gamete receives one allele. In other words, an individual inherits one allele for each trait from each parent.

Here’s how it works:

1.	Each individual has two alleles for each gene, one inherited from their mother and one from their father.
2.	These two alleles may be the same (homozygous) or different (heterozygous) versions of the gene.
3.	During the formation of gametes, the two alleles segregate, and each gamete carries only one allele.
4.	When fertilization occurs, with one gamete from each parent combining, the offspring inherits one allele from each parent, re-establishing the diploid number of alleles.

Question 11

Mendel’s law of independent assortment

Answer 11

Genes found on different chro­ mosomes are sorted into sex cells independently of one another

Question 12

linkage

Answer 12

Genes that are found on the same chromosome are said to be linked. The closer together two genes are on a chromosome, the greater the linkage and the less likely they are to be separated during crossing over.

Question 13

sickle cell disease.

Answer 13

An autosomal recessive disease caused by a point mutation in an allele that codes for one of the polypeptide chains of the hemo­ globin protein

Question 14

point mutation

Answer 14

n A change in the base sequence of a gene that results from the change of a single base to a different base.

Question 15

autosomal recessive disease

Answer 15

A disease caused by a recessive allele; one copy of the allele must be inherited from each parent for the disease to develop.

Question 16

insertion mutation

Answer 16

A change in the base sequence of a gene that results from the addition of one or more base pairs in the DNA.

Question 17

deletion mutation

Answer 17

A change in the base sequence of a gene that results from the loss of one or more base pairs in the DNA.

Question 18

trinucleotide repeat diseases

Answer 18

A family of autosomal dominant diseases that is caused by the insertion of multiple copies of a three­base­pair sequence (CAG) that codes for the amino acid glu­ tamine. Typically, the more copies inserted into the gene, the more serious the disease.

Question 19

autosomal dominant disease

Answer 19

A disease that is caused by a domi­ nant allele: Only one copy needs to be inherited from either parent for the disease to develop.

Question 20

X-linked disorders

Answer 20

Genetic conditions that result from mutations to genes on the X chromosome. They are almost always expressed in males, who have only one copy of the X chro­ mosome; in females, the second X chromosome containing the nor­ mally functioning allele protects them from developing X­linked disorders.

Question 21

qualitative variation

Answer 21

Phenotypic variation that can be characterized as belonging to dis­ crete, observable categories.

Question 22

quantitative variation

Answer 22

Phenotypic variation that is char­ acterized by the distribution of continuous variation (expressed using a numerical measure) within a population (for example, in a bell curve).

Question 23

polygenic traits

Answer 23

Phenotypic traits that result from the combined action of more than one gene; most complex traits are polygenic.

Question 24

pleiotropy

Answer 24

The phenomenon of a single gene having multiple phenotypic effects.

Question 25

heritability

Answer 25

The proportion of total phenotypic variability observed for a given trait that can be ascribed to genetic factors.

Question 26

phenylketonuria (PKU)

Answer 26

Autosomal recessive condition that leads to the accumulation of large quantities of the amino acid phenylalanine, causing mental retardation and other phenotypic abnormalities.

Question 27

Monohybrid

Answer 27

Crossing 2 plants that differ in only one characteristic.

Question 28

Dihybrid

Answer 28

Crosses where the parent plants differed in 2 different characteristics.

Question 29

• Mendel’s 3 main principles.

Answer 29

1) The Principle of Segregation
* Offspring inherit one discrete factor for a trait from each parent.
* These factors maintain their unique integrity from generation to generation.
2) The Principle of Dominance and Recessiveness
* Some expressions of a specific trait were dominant over others.

3) The Principle of Independent Assortment * Different traits were not inherited together as packages. They passed from generation to generation as independent units.

Question 30

• The problems with Mendel’s research and his conclusions.

Answer 30

Mendel lucked out … First of all, he happened to have selected traits that are influenced by single genes in the chromosomes of pea plants. These are called monogenic traits. Problems … Polygenic traits?

Secondly: Some of Mendel’s results were contrary to his principle of independent assortment.

Thirdly: The traits Mendel examined were types that are expressed as discrete categories … … one thing OR another. There are traits which are continuous in their potential forms … eg. Height among people. Skin colour- many shades of skin colour.

Question 31

Blending of Traits’

Answer 31

19th Century Views of Inheritance

Molecular biology was not discovered until the 20th century.
Darwin did not understand how traits were being passed.
When Darwin published it was thought that there was a blending of traits.

Question 32

Breeding or Artificial Selection

Answer 32

Selection people select for desirable traits in plants or animals rather than nature doing the selecting. Eg corn, dogs… 6000 years ago in the Americas.

Question 33

Gregor Mendel (1822–1884)

Answer 33

1850s Research on plant hybridization: how do new varieties of domesticated plants (or breeds of domesticated animals) come about?
This is right at the same time Darwin is publishing Origin, and the first neandertal skull is found sparking debates on evolution.
He made a chart of pea plant traits, and noticed patterns that helped him to identify underlying mechanisms of plants.
Peas with wrinkled and smooth seeds, he noticed that what the first generation had, the third generation would have some of these traits. Even hybrids carry both versions of the traits.

Question 34

Each plant contains 2 ‘factors’ for a trait: Mendel’s Hypothesis

Answer 34

when crossing 2 hybrid plants, there is a 50:50 chance that each parent’s contribution will be one factor or the other, which means 4 possible combinations in their offspring:

• When crossing 2 plants they randomly passed on one factor OR the other to each offspring One parent can only give a dominant factor and one can only give the recessive factor.
• When crossing 2 pure strain plants that differ in a trait, each offspring will receive a dominant and a recessive factor for that trait: all offspring will be hybrids for that trait.

Question 35

How and when life first appeared

Answer 35

3.8 billion years ago as Prokaryotic Cells – single cells no nucleaus
Eukaryotic Cells- ≈ 2.0 billion years ago DNA is separated from the rest of the cell by a nucleus. Started as a single cell organism.
600 million years ago the first fossils that seem like animals

Question 36

Basic Animal Cell Structure

Answer 36

mitochondria – responsible for energy of the cell

nucleus – houses DNA

endoplasmic reticulum – folded membranes which increase the area where protein synthesis can occur.
plasma
membrane- outer boundary of the cell, involved in communicating activity between cell.

Cytoplasm- provides support for organelles,

ribosomes – where proteins are synthesized from amino acids.

Question 37

Somatic Cells

Answer 37

all tissues of the body are made from this- blood, muscle, nerve etc.

Question 38

Sex Cells (gamet)

Answer 38

play no part in the physical body, transport generic information from one generation to the next.

Question 39

Nitrogenous Bases:

Answer 39

(A)Adenine
(G) Guanine
(T) Thymine
(C) Cytocine
8 “Base Pairs”

Question 40

How many base pairs in A single copy of nuclear DNA

Answer 40

3,200,000,000

Question 41

diploid number

Answer 41

Humans normally have 46 chromosomes: this is referred to as our diploid number.

• These occur as 23 pairs of matched chromosomes.
• Of each pair, one comes from the father and one from the mother.
• Each pair is called homologous chromosomes or a ‘homologous pair’.
  The last set are called sex chromosomes because they determine whether the person’s sex will be male or female.

Question 42

Chromosomes

Answer 42

different sections of the entire DNA sequence

Question 43

A gene

Answer 43

a set sequence of base pairs (out of the whole DNA sequence) that codes for a specific protein

Question 44

Alleles

Answer 44

Alleles are different versions of a specific trait – (slightly) different coding at the same gene location (Mendel’s ‘particles’).
* For each gene you will receive two alleles, one from each parent - these can be different or the same.
* Different alleles may code for conflicting traits (e.g. blood type O versus type A). 18 The physical expression of a trait depends on which allele is dominant and on how many genes are involved in expressing that trait - whether it’s a monogenic or polygenic trait.

Question 45

mitosis

Answer 45

Somatic cell replication

Question 46

meiosis

Answer 46

Sex cell replication

Question 47

haploid number

Answer 47

Sex Cells A sex cell carries only half the chromosomes needed to create a normal individual: 23
* This is the haploid number of chromosomes.
* Need to join 1 male and 1 female gamete in order to have the required diploid number of chromosomes in an embryo and the complete genetic blueprints for a normal individual.

Question 48

Oogenesis vs Spermatogenesis:

Answer 48

In summary, oogenesis and spermatogenesis are the processes of gamete production in females and males, respectively. They differ in terms of location, timing, meiotic divisions, and the size and motility of the gametes produced. Oogenesis results in the formation of a single, non-motile egg cell, while spermatogenesis leads to the production of multiple, highly motile sperm cells. These processes are essential for sexual reproduction in most sexually reproducing organisms.

50% that resulting zygote will be a boy or a girl.

Question 49

Gene pool:

Answer 49

All the different genes and their various expressions (alleles) that exist in the DNA of a species or population.

Question 50

Genotype

Answer 50

The genetic makeup of an individual. This can refer to their entire genetic makeup or to the alleles found at specific gene locations.

Question 51

Phenotype

Answer 51

The physical expression of an individual’s genotype.

Question 52

A good definition of evolution

Answer 52

“A change in allele frequency in a population from one generation to the next.” Change, however slight in our species over time.

Question 53

Two components to the evolutionary process:

Answer 53

1. The creation of genetic variability in individuals (Premise #2) upon which the evolutionary process can act.
2. External factors that act upon individuals’ genetic variability: the process of evolution.

Question 54

Sources of genetic variability upon which evolution can act:

Answer 54

-Changes in allele frequencies
* New combinations of alleles
* Formation of new alleles

Recombination
a. Random assortment of chromosomes
b. Crossing-over

Question 55

Number of genetically different individuals that can potentially result from one egg being fertilized is

Answer 55

8,324,608 x 8,324,608 = c. 69,299,000,000,000!!

Question 56

% of our genome is the same as chimps and bonobos.

Answer 56

98%

Question 57

Random mutations

Answer 57

the only source of new alleles all other alleles already exist and are combined.

Question 59

Inheritance
Let’s assume two versions of a gene: A and a. When two people have a child, there are several possibilities.

Answer 59

Both parents are AA: All of their children will be AA as well (homozygous for AA).

Both parents are aa: All of their children will be aa as well (homozygous for aa).

One parent is Aa and another parent is Aa: Their child has a 25 percent chance of being AA (homozygous), a 50 percent chance of being Aa (heterozygous), and a 25 percent chance of being aa (homozygous)

One parent is Aa and the other is aa: Their child has a 50 percent chance of being Aa (heterozygous) and a 50 percent chance of being aa (homozygous).

One parent is Aa and the other is AA: Their child has a 50 percent chance of being AA (homozygous) and a 50 percent chance of being Aa (heterozygous).

Question 60

tetrads

Answer 60

Crossing-over
occurs during
meiosis when
double strands
come together
to form tetrads.

An allele that
came from your
father ends up in
a chromosome
that came from
your mother