Lecture 6 Flashcards
1
Q
Genetics
A
Heredity and variation of
organisms, the genetic makeup and phenomena of an organism, type, group, or condition
2
Q
Genomics
A
The study of genes and their functions, and related techniques
3
Q
Epigenetics
A
The study of heritable changes in gene function that do not involve changes in DNA sequence
4
Q
DNA (DEOXYRIBONUCLEIC ACID)
A
- Contains the instructions for growth and development in humans and all living things.
- Packaged into chromosomes that contain all of our genes.
5
Q
RNA (RIBONUCLEIC ACID)
A
A form of nucleic acid with generally 1 strand only, unlike the double strand of DNA
6
Q
CHROMOSOMES
A
Thread like structures found in cells, containing DNA and other supporting structures, and
contain the genetic information about the individual.
7
Q
GENES
A
- The basic physical and functional unit of
heredity. - Genes are made up of DNA.
8
Q
Where is DNA located?
A
Cell nucleus but also mitochondria
9
Q
What makes up and is the shape of DNA?
A
Comprises many sets of base pairs:
*Adenine
*Thymine
*Guanine
*Cytosine
- Each base is attached to a sugar molecule and a phosphate molecule.
- Double helix shaped
10
Q
Human DNA
A
- About 3 billion bases
- > 99% of those bases are the same in all people
11
Q
What are the types of DNA?
A
- Coding DNA
- Noncoding DNA
12
Q
Coding DNA
A
The genes in the coding DNA transcribe, producing
mRNAs, which subsequently undergo translation,
producing proteins
13
Q
Noncoding DNA
A
- Does not provide instructions for making proteins.
- But some noncoding DNA are integral to the function of cells, particularly the control of gene activity.
14
Q
Coding vs Noncoding DNA
A
15
Q
Nucleotide
A
Comprises 1 base, 1 sugar molecule and 1 phosphate molecule.
16
Q
Codon
A
- A specific sequence of three
consecutive nucleotides - Part of the genetic code and that specifies a particular amino acid in a protein or starts or stops protein synthesis
17
Q
What are the types of RNA?
A
- mRNA
- tRNA
- Ribosomal RNA
- Others eg miRNA (micro RNA), siRNA (small interfering RNA), lncRNA (long non-coding RNA)
18
Q
mRNA
A
- Messenger RNA
- Synthesised in the nucleus by the process of transcription.
- It takes information from DNA in the nucleus to the ribosomes
19
Q
tRNA
A
- Transfer RNA
- Found in the cytoplasm
- Main function is to transfer of amino acids during protein synthesis
- Essential component of translation
20
Q
Ribosomal RNA
A
- These are the major component of ribosomes
- the protein/RNA complexes responsible for assembling proteins from the mRNA code
- It accounts for the majority of the RNA present in the cell at any given time.
21
Q
What happens during DNA replication?
A
DNA makes an exact copy of itself—1 set becomes 2.
22
Q
What is transcription?
A
DNA is used to make messenger RNA (mRNA).
23
Q
What happens to mRNA before it leaves the nucleus?
A
Unneeded parts are removed; the important parts go to the cytoplasm.
24
Q
What is translation?
A
In the cytoplasm, mRNA is read and used to build proteins with help from transfer RNA (tRNA).
25
How is the message in RNA read?
In 3-letter codes called codons.
26
What do codons code for?
Specific amino acids, which are the building blocks of proteins.
27
How many amino acids are there?
20 different amino acids.
28
Can more than one codon code for the same amino acid?
Yes, most amino acids have more than one codon.
29
What is a chromosome made of?
DNA tightly coiled around proteins called histones.
30
What supports the structure of DNA in chromosomes?
Histones, which are special proteins.
31
What is the centromere?
It's a constriction point that divides the chromosome into two arms.
32
What are the two arms of a chromosome called?
The short arm is the p arm, and the long arm is the q arm.
33
What does the location of the centromere determine?
The chromosome's shape and helps identify gene locations.
34
Locus
The site where a specific gene is found
35
What do some genes do?
They give instructions to make proteins.
36
Do all genes make proteins?
No, many genes do not code for protein
37
How big can human genes be?
They range from a few hundred to over 2 million DNA bases.
38
How many genes do humans have?
Around 20,000 to 25,000 genes.
39
How many copies of each gene does a person have?
Two—one from each parent.
40
Are all genes the same in every person?
Most are, but less than 1% are slightly different.
41
What is an allele?
A version of a gene with small differences in the DNA.
42
What do alleles contribute to?
A person's unique physical traits.
43
Genotype
- The collection of genes that an individual possesses
or
- The 2 alleles at a particular locus
44
Phenotype
- Refers to how the genotype is expressed
- Recognisable trait
45
Mutations
Change that occurs in our DNA sequence, either due to mistakes when the DNA is copied or as the result of environmental factors
46
Genetic disease
Any disorder which involves the
genetic makeup of an individual.
- Hereditary
- Acquired
47
Hereditary disease
Transmitted from the parents
48
Congenital disease
- Refers to a disorder which is present at birth.
- It may be hereditary or acquired in utero
49
Types of Genetic Disorders
1. Chromosomal defects
2. Mendelian gene defects
3. Multifactorial inheritance disorders
50
Chromosomal Defects
Characterized by the presence of either abnormal chromosomes or abnormal
chromosome numbers.
- Polyploidy
- Aneuploidy
- Deletion
- Repetition
51
Polyploidy
Having a multiple of the normal
chromosome numbers.
* It is a cause of early miscarriage
52
Aneuploidy
Abnormality of chromosome numbers, but does not involve a multiple of the number of genes.
* There may be the addition of an additional autosome or
sex chromosome, or the absence of an autosome or sex
chromosome.
53
Trisomy-21 (Down syndrome):
an additional chromosome
21
54
Trisomy 18 (Edwards' syndrome):
an additional chromosome 18
55
Turner’s syndrome (XO):
1 sex chromosome only
56
Kleinfelter’s syndrome (XXY):
an additional sex chromosome
57
Prader-Willi syndrome:
deletion of a part of the
short arm of paternal chromosome 15
58
Mendelian disorders
Gene defects and are usually a result of mutations in DNA sequences.
* Normal chromosome numbers in cells
They can be described as:
* Autosomal dominant disorders
* Autosomal recessive disorders
* X-linked inheritance (usually recessive)
disorders
59
Autosomal dominant disorders
If the offspring receives just one of the affected genes, they will manifest the disease.
Examples:
- Achondroplasia
- Marfan’s syndrome,
- Huntington’s Disease,
- Neurofibromatosis,
- Some types of Ehler’s Danlos syndrome
60
Autosomal Recessive Disorders
- These require the individual to have the abnormal gene from both parents, in order to manifest the disease.
- Receiving one abnormal gene will make them a ‘carrier’, but not have the disease.
Examples:
- Cystic fibrosis
- albinism
- Tay-Sachs disease
- Phenylketonuria
61
X-Linked Inheritance Disorders
- The abnormal gene is carried on the X chromosome.
Examples:
- Haemophilia A
- Haemophilia B
62
Penetrance
Probability that the person
with the abnormal genotype actually develops the
disorder.
63
Expression of the disorder
How the disease is
expressed in that individual
64
Multifactorial inheritance disorders
Disorders which involve defects in a number of different genes in addition to the influence by various environmental factors.
Examples:
- Hypertension
- Diabete mellitus
65
What is genetics?
A branch of biology that deals with the heredity and variation of organisms.
## Footnote
It includes the genetic makeup and phenomena of an organism, type, group, or condition.
66
Define genomics.
The study of genes and their functions, and related techniques.
## Footnote
Source: WHO
67
What does epigenetics study?
Heritable changes in gene function that do not involve changes in DNA sequence.
## Footnote
It focuses on changes in gene expression.
68
What is DNA?
DNA contains the instructions for growth and development in humans and all living things, packaged into chromosomes that contain all of our genes.
## Footnote
DNA stands for deoxyribonucleic acid.
69
How many strands does RNA typically have?
Generally 1 strand only.
## Footnote
RNA stands for ribonucleic acid.
70
What are chromosomes?
Thread-like structures found in cells, containing DNA and other supporting structures, and contain the genetic information about the individual.
71
Define a gene.
The basic physical and functional unit of heredity, made up of DNA.
## Footnote
Some genes act as instructions to make proteins.
72
Where is DNA located?
Primarily in the cell nucleus, but also found in the mitochondria.
73
What shape does DNA take?
A double helix.
74
What are the four bases of DNA?
* Adenine
* Thymine
* Guanine
* Cytosine
75
What is the significance of the base pairing in DNA?
Adenine always joins with thymine, whereas guanine always joins with cytosine.
76
How many bases does human DNA consist of?
About 3 billion bases.
77
What percentage of DNA is made up of protein-coding genes?
About 1 percent.
78
What is noncoding DNA?
DNA that does not provide instructions for making proteins, previously thought to be 'junk'.
79
What is a nucleotide composed of?
1 base, 1 sugar molecule, and 1 phosphate molecule.
80
What is a codon?
A specific sequence of three consecutive nucleotides that specifies a particular amino acid in a protein or starts or stops protein synthesis.
81
What is mRNA?
Messenger RNA, synthesized in the nucleus by transcription, taking information from DNA to the ribosomes.
82
What is the role of tRNA?
Transfer RNA, found in the cytoplasm, attaches to amino acids and pairs with codons on mRNA during protein synthesis.
83
What happens during DNA replication?
An identical copy of DNA is made.
84
What does the term 'translation' refer to?
The process where mRNA interacts with tRNA to make proteins.
85
How many chromosomes are there in human cells?
46 chromosomes (23 pairs).
86
What are autosomes?
22 pairs of chromosomes that are not sex chromosomes.
87
What is a locus?
The specific site where a gene is found on a chromosome.
88
Define genotype.
The collection of genes that an individual possesses or the alleles at a particular locus.
89
What is phenotype?
The expression of the genotype, such as traits like eye color or hair color.
90
What is the difference between dominant and recessive alleles?
Dominant alleles mask the effects of recessive alleles; dominant is denoted by uppercase letters and recessive by lowercase letters.
91
What is a mutation?
A change in the DNA sequence, either due to copying errors or environmental factors.
92
What are hereditary mutations?
Mutations inherited from a parent and present in every cell of the body.
93
What are acquired mutations?
Mutations not passed on from parents, resulting from environmental stressors or errors during cell division.
94
What can be the effects of mutations?
* No effect
* Abnormal protein formation
* Development of diseases
* Beneficial adaptations
95
What is a genetic disease?
Any disorder involving the genetic makeup of an individual
96
How does genetic disease differ from hereditary disease?
Genetic disease may be transmitted from parents (hereditary) or acquired after birth
97
What is a congenital disease?
A disorder present at birth, which may be hereditary or acquired in utero
98
List the types of genetic disorders
* Chromosomal defects
* Mendelian gene defects
* Multifactorial inheritance disorders
99
What characterizes chromosomal defects?
Abnormal chromosomes or abnormal chromosome numbers
100
What is polyploidy?
Having a multiple of the normal chromosome numbers
101
What is aneuploidy?
An abnormality of chromosome numbers not involving a multiple of the number of genes
102
Give an example of a chromosomal defect
Trisomy-21 (Down syndrome)
103
What are Mendelian disorders?
Gene defects usually resulting from mutations in DNA sequences
104
Define autosomal dominant disorders
Disorders where one affected gene from a parent manifests the disease
105
What is the expected outcome for offspring of an autosomal dominant disorder carrier?
50% affected, 50% unaffected
106
What are autosomal recessive disorders?
Disorders requiring abnormal genes from both parents to manifest
107
What is the expected outcome for offspring of two carriers of an autosomal recessive disorder?
25% affected, 50% carriers, 25% normal
108
What are X-linked inheritance disorders?
Disorders where the abnormal gene is carried on the X chromosome
109
What is the inheritance pattern for X-linked recessive disorders?
Males affected if they inherit the abnormal X chromosome from their mother
110
Give an example of an X-linked inheritance disorder
Haemophilia A
111
What is penetrance?
The probability that a person with an abnormal genotype develops the disorder
112
What does expression of a disorder refer to?
How the disease is expressed in an individual (the phenotype)
113
Define multifactorial inheritance disorders
Disorders involving defects in multiple genes and influenced by environmental factors
114
What is an example of a multifactorial inheritance disorder?
Hypertension
115
What factors influence the risk of developing multifactorial inheritance disorders?
* Lifestyle choices
* Number of family members affected
* Genetic relatedness
* Gender
116
True or False: Familial disorders are always hereditary.
False
117
Fill in the blank: The combination of genetic predisposition and _______ can determine if a disorder will manifest.
environmental stressors
