Lecture 4 - Genetics and Inheritance

Question 1

genetic information

Answer 1

• DNA sequences on chromosomes
• Sequences that code for proteins (called genes)

Question 2

genes

Answer 2

• segments of DNA sequence on chromosomes
• code for a specific protein (polypeptide) that will play a structural and functional role in cell
• 2 copies (alleles)

Question 3

Trait (phenotype)

Answer 3

• physical characteristics
  (internal/external)
• produced by the action of proteins made from genes

Question 4

alleles

Answer 4

• 2 copies of genes
• each inherited from 1 parent
• can produce different characteristics of the trait they determine
  ex: blood types

Question 5

homozygous

Answer 5

genes with 2 copies of the same allele

Question 6

heterozygous

Answer 6

genes with two different alleles

Question 7

dominant

Answer 7

when only one copy is needed for effect to be seen

Question 8

recessive

Answer 8

when 2 copies are needed for effect to be seen

Question 9

genotype

Answer 9

the alleles in an individual

Question 10

phenotype

Answer 10

the physical expression in words

Question 11

examples of dominant traits

Answer 11

• unattached ear lobes
• freckles
• rolling the tongue

Question 12

albinism

Answer 12

• recessive disorder
• enzyme is missing so reduced ability to produce brown pigment melanin

Question 13

dominant allele

Answer 13

produces functional enzyme

Question 14

recessive allele

Answer 14

produces non-functional enzyme

Question 15

law of segregation

Answer 15

During meiosis and gamete formation, the two alleles for
each gene separate as the pair of chromosomes
separate and move toward opposite ends of the cell

Question 16

Law of Independent Assortment

Answer 16

Each chromosome is inherited independently of the other
chromosomes

Question 18

complete dominance

Answer 18

Heterozygote (Aa) exhibits the trait
associated with the dominant allele but not
that of the recessive allele

Question 19

Codominance

Answer 19

Effects of both alleles are apparent in a heterozygote
ex: AB blood type

Question 20

Incomplete dominance

Answer 20

Physical characteristics in between a homozygous
dominant and homozygous recessive individual

Question 21

Environmental Influences

Answer 21

Ex. Himalayan rabbit
-lower body
temperature in
early development
in certain areas of
body leads to
darkening of fur

Question 22

Pleiotropy

Answer 22

When a gene influences more than one trait (ex: marfan syndrome)

Question 23

Polygenic inheritance (dominant / recessive)

Answer 23

• Variation in a trait, such as height/Intelligence
• Involves 2 or more genes

Question 24

causes of mutations (breaks of chromosomes)

Answer 24

• Chemicals
• Radiation
• Viruses (rarely)

Question 25

results of mutations

Answer 25

- Results in changes in the structure and function of a whole chromosome - Can cause serious damage if passed on to child - Few of these lead to live births as they are too damaging

Question 26

deletion

Answer 26

Loss of tip of chromosome 5

Question 27

duplication

Answer 27

ex: Fragile X syndrome

Question 28

when is prenatal genetic testing recommended

Answer 28

Prenatal genetic testing is recommended when: ▪ a defective gene runs in the family ▪ Or when the mother is older than 35

Question 29

prenatal genetic tests

Answer 29

Chorionic Villus Sampling (CVS) can be done at 11-12 weeks * Amniocentesis done at >15 weeks

Question 30

Chorionic villi sampling (CVS)

Answer 30

▪ Involves taking a small piece of chorionic villi ▪ Cells have same genetic makeup as fetus ▪ Cells are cultured and then chromosomes examined ▪ → karyotyping possible -look for abnormalities in the # of chromosomes

Question 31

Amniocentesis

Answer 31

10–20 ml of amniotic fluid is withdrawn, which contain epithelial cells of the fetus ▪ Cells are cultured (>more cells) and then examined ▪ 1. karyotyping -look for abnormalities in the # of chromosomes ▪ 2. DNA can be extracted & analyzed if disease gene is known

Question 32

phenylketonuria (PKU)

Answer 32

results in poor development of the nervous system & profound mental retardation

Question 33

what cause PKU

Answer 33

▪ Due to a missing enzyme ▪ Phenylalanine →an amino acid accumulates

Question 34

Pedigrees

Answer 34

Chart showing the genetic connections among individuals in a family

Question 35

causes of genetic disorders

Answer 35

- recessive alleles - when both parents are heterozygous

Question 36

Carrier

Answer 36

=someone who displays the dominant phenotype but is heterozygous for a trait: Aa -carries the recessive allele & can pass it on