Genetics

Question 1

Define inheritance

Answer 1

Passing of hereditary traits from one generation to the next

Question 2

What is the difference between genotype and phenotype?

Answer 2

Genotype 
The genetic makeup of an organism
Can be determined by observing DNA
Completely depends on gene sequences 
Inherited by offspring

Phenotype
Visual properties and behaviours of the organism
Determined by observing outward characteristics
Depends on genotype and environmental factors
Not inherited by offspring

Question 3

What are homologous chromosomes?

Answer 3

Homologous chromosomes are the chromosomes which contain alleles for the same type of genes (both look the same)

Question 4

What are non-homologous chromosomes?

Answer 4

Non-Homologous chromosomes are chromosomes that contain alleles for different type of genes

Question 5

What is an allele?

Answer 5

A different form of the same gene

BB dominant
bb recessive

Question 6

What is homozygous?

Answer 6

A person with the same alleles on both chromosomes

Question 7

What is heterozygous?

Answer 7

Having different alleles on homologous chromosomes

Heterozygous individuals are carriers of a recessive gene

Question 8

What type of genotype leads to PKU?

Answer 8

Homozygous recessive

Question 9

What is the term for fraternal twins and how are they formed?

Answer 9

Dizygotic

The independent release of 2 oocytes (cells in the ovary) fertilized by 2 separate sperm

Question 10

What is the term for identical twins and how are they formed?

Answer 10

Monozygotic

2 individuals that develop from a single fertilized ovum
genetically identical & always the same sex

If ovum does not completely separate, conjoined twins (share body structures)

Question 11

Name the 4 types of bases that make up a strand of DNA

Answer 11

Tymine (T)

Adenine (A)

Guanine (G)

Cytosine (C)

Question 12

How many chromosomes do human body cells contain?

Answer 12

46 chromosomes

23 pairs

Question 13

What are chromosomes made of?

Answer 13

DNA

Question 14

What is the term/name of chromosomes 1-22?

Answer 14

Autosomes

Question 15

What is the 23rd pair of chromosomes called?

Answer 15

Sex chromosomes

XX = Female
XY = Male

Question 16

What is a karyotype?

Answer 16

A pattern of either a male or female chromosomes

46, XY = Male
46, XX = Female

Question 17

What chromosomes is the gene for cystic fibrosis located?

Answer 17

Chromosome 7

Question 18

What chromosomes is the gene for sickle cell disease located?

Answer 18

Chromosome 11

Question 19

What type of order are genes arranged in on a chromosome?

Answer 19

Linear

Question 20

Define nondisjunction

Answer 20

Chromosomes fail to separate properly

Cell with one or more extra or missing chromosomes is called an aneuploid
(2n-1) is missing a chromosome
(2n+1) has an extra chromosome

Question 21

Define aneuploid

Answer 21

Cell with one or more extra or missing chromosomes

Question 22

Define translocation

Answer 22

Location of chromosome segment is moved

Crossing-over between 2 nonhomologous chromosomes

Down syndrome results from a portion of chromosome 21 becoming part of another chromosome

Individuals have 3 copies of that part of chromosome 21

Question 23

3 most common autosome anomalies

Answer 23

Down syndrome (trisomy 21: 47,XX,+21)

Edwards syndrome (trisomy 18: 47,XX,+18)

Patau syndrome (trisomy 13: 47,XX+13)

Question 24

2 most common sex chromosome anomalies

Answer 24

Turner syndrome 45,X

Klinefelter syndrome 47,XXY

Question 25

What causes down syndrome?

Answer 25

Nondisjunction of chromosome 21 (trisomy 21) More common in older mothers due to more exposure to radiation & chromosome-damaging chemicals 1 in 800 infants is born with Down syndrome mental retardation, distinctive facial structures & malformation of the heart, ears, hands & feet

Question 26

Define mutation

Answer 26

An alteration or change in the genetic material

Question 27

Causes of a mutation

Answer 27

Inherited Exposure to mutagenic agents Spontaneously through errors in DNA replication/repair

Question 28

What is amniocentesis? Describe the process? At how many weeks?

Answer 28

Pre-natal diagnosis to detect chromosome abnormalities Take 10-20 ml amniotic fluid at 15-17 weeks gestation A syringe inserted through the abdomen under ultrasound guidance Foetal cells cultured for chromosome analysis Risk of miscarriage about 0.5%; small risk of infection If termination- labour is induced

Question 29

Why would someone get a prenatal diagnosis?

Answer 29

Avoid birth of affected baby eg with Down Syndrome Know in advance & prepare for birth/treatment Relieve uncertainty

Question 30

Define genes

Answer 30

Genes are codes for cells to make proteins Genes are located on chromosomes

Question 31

The term for alterations in single genes

Answer 31

Single gene disorder

Question 32

The term for variants in genes

Answer 32

Multifactorial disease (+environment)

Question 33

Chromosomal imbalance term

Answer 33

Chromosome disorder

Question 34

What are the 3 types of single gene disorders?

Answer 34

Autosomal dominant - always expresses itself Autosomal recessive - only expresses in the absence of dominant unaltered gene – healthy carrier X-linked - genes found on X chromosomes

Question 35

Define autosomal dominant, recissive and x-linked recissive

Answer 35

Dominant These individuals are called Heterozygotes with one copy of the altered gene they are affected Recessive Homozygotes must have two copies of the altered gene to be affected X-linked recessive Males with an altered gene on the X-chromosome are always affected

Question 36

Name 3 audtosomal dominant conditions

Answer 36

Huntington disease Neurofibromatosis type 1 Marfan syndrome Familial hypercholesterolemia Familial Adenomatous Polyposis (FAP) Prader-willi

Question 37

Name 3 autosomal recissive conditions

Answer 37

Sickle Cell disease Cystic fibrosis Batten Disease Congenital deafness Phenylketonuria (PKU) Spinal muscular atrophy Recessive blindness Maple syrup urine disease

Question 38

Signs of Marfan syndrome

Answer 38

Tall stature Elongated thin limbs and fingers High risk of heart defects Disloacted lens

Question 39

Signs of sickle disease

Answer 39

Abnormal haemoglobin | Bony infarcations in the phalanges and metacarpals can result in unequal finger length

Question 40

Name 3 x-linked recissive conditions

Answer 40

Fragile X syndrome Haemophilia Duchenne muscular dystrophy (DMD) (Becker BMD) Fabry disease Retinitis pigmentosa Alport syndrome Hunter syndrome Ocular albinism Adrenoleucodystrophy

Question 41

Signs of Fragile x syndrome

Answer 41

Causes mental retardation in some of males with this gene learning disabilities, oversized ears, enlarged testes & double jointedness may be involved with autism Unaffected males may pass gene onto daughters whose children may suffer

Question 42

Name 4 common polygenic disorders

Answer 42

Alzheimer's Diabetes Cancer Eczema

Question 43

Define multifactorial inheritance

Answer 43

Inheritance controlled by many genes plus the effects of the environment

Question 44

The term for environmental influences that cause development defects

Answer 44

Teratogens

Question 45

Name 3 teratogens and what they affect

Answer 45

Chemicals & Drugs Fetal alcohol syndrome = slow growth, facial features, defective heart & CNS Cocaine = attention problems, hyperirritability, seizures Cigarette Smoking Low birth weight, cleft lip & palate, SIDS Irradiation or radioisotopes during the first trimester Mental retardation, microcephaly