DNA and Genetics 2022 Flashcards
1
Q
DNA
A
- DeoxyriboNucleic Acid
- ‘Blueprint of life’
- Long and complex molecule, made up of many atoms; found in nucleus of our cells; hereditary material; contains all of the information necessary for an organism to develop, survive, and reproduce
2
Q
Nucleus in terms of DNA
A
- ‘Control centre’; master set of instructions for a cell
- Controls what cell will become, how well it functions and how long it will live
3
Q
Cells
A
- Basic unit of life
- Provide structure for the body, take in nutrients from food, convert those nutrients into energy, and carry out specialized functions
- Nucleus, control centre; surrounded by cytoplasm; has internal structures called organelles
4
Q
Examples of key organelles
A
- Mitochondria
- Plastids
- Vacuoles
- Chloroplast (plant)
5
Q
Major differences between plant and animal cell
A
- Plant cells have cell wall and membrane, chloroplast and unique rectangular shape
- Animal cells have a cell membrane but no cell wall
6
Q
What is DNA made up of?
A
- DNA is stored as a code, through chemical building blocks called nucleotides; made up of four chemical nitrogenous bases:
1. Adenine
2. Thymine
3. Guanine
4. Cytosine
7
Q
Nitrogenous base pairing
A
- Adenine and Thymine
- Guanine and Cytosine
- Paired together by hydrogen bonds
- Human DNA consists about 3 billion bases, 99% are the same, it is the 1% which determines all our differences.
8
Q
Describe the physical structure of DNA
A
- Double helix
- Rungs: two nitrogen bases paired by hydrogen bonds; upright sides: alternating sugar and phosphate groups
9
Q
What do genes do?
A
- Carries the information that determines your traits
- Genes are DNA sequences; they are converted into messages to produce proteins; complex molecules that consist of amino acids; essential to human life, allows us to survive e.g enzymes, hormones, and antibodies
- DNA sequences regulate when, how, and how much of a protein is made.
10
Q
What is a gene?
A
- Basic unit of heredity passed from parent to child
- Made up of DNA sequences; of nucleotide bases that code for a specific physical and biological trait.
- Humans have approximately 20,000 genes
- Genes are located on chromosomes in specific spots
11
Q
How do genes fit in the nucleus?
A
- DNA is condensed; coiled and compacted to form chromosomes
1. DNA binds to proteins known as histone
2. DNA + histones coil to form structures like beads on a chain
3. This is compacted into a chromosome
12
Q
What is a chromosome?
A
- Carries genetic material of an organism
- In the nucleus of each cell, DNA molecule is packaged into thread-like structures called chromosomes
- Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure
- Each cell nucleus contains about 2m of DNA
13
Q
Number of human chromosomes
A
Humans = 46 Chromosomes (somatic/body cells)
You get 23 chromosomes from each parents gametes.
14
Q
What are non sex chromosomes called?
A
- Autosomes
- Non-sex chromosomes: 44 chromosomes/22 pairs
15
Q
Sex chromosomes
A
- 23rd pair of chromosomes: sex chromosomes
- Female: XX
- Male: XY
16
Q
Fertilisation process
A
- 23 chromosomes in sperm + 23 chromosomes in egg = 46 chromosomes in each human cell
- Offspring (zygote) is produced; single cell
- Zygote inherits 1 copy of each chromosome from mother, and 1 copy from father; offspring inherits genes from both parents
17
Q
What are sex cells called?
A
- Sex cells/reproductive cells are called gametes
18
Q
Genetics
A
- Study of heredity and natural variation
- Gregor Mendel
19
Q
Heredity
A
- The study of how traits and characteristics are passed down and inherited from parent to offspring
20
Q
Natural variation
A
- No two living things are identical, differences observed are variations; variations are result of the combined effect of inherited characteristics and environment
21
Q
How are traits inherited?
A
- Features or traits that are inherited are passed from one generation to next in form of genetic code; this code is written in molecule of DNA found in the nucleus of cells.
- In every human, chromosomes come in pairs/homologous pairs: maternal + paternal
- For every gene in your body, there are two alleles; one maternal and one paternal; or two versions of said gene that are passed onto offspring separately
22
Q
Relationship between genes and alleles
A
- Gene is a portion of DNA that determines a certain trait; they are responsible for expression of traits in an organism; genes are the characteristic (e.g. eye colour)
- An allele is a specific form of a gene; they are responsible for the variations in which a given trait can be expressed; alleles are variations of the gene (e.g. blue, brown, green etc.)
- 1 gene, two different alleles
23
Q
Genotype
A
- An individual’s collection of genes; refers to the two alleles inherited for a particular gene
24
Q
Phenotype
A
- The observable, physical properties of an organism; this can include appearance, development, and behaviour; it is determined by the genotype
25
Dominant Alleles
- Dominant alleles mask the effect of the other allele. (Shown as the uppercase letter)
26
Recessive alleles
- Hidden or masked by the dominant allele
- Although it is not physically expressed, it is still there
27
Types of alleles
- Homozygous Dominant: BB = Plant has two dominant
- Heterozygous: Bb: Law of genetics; will only see dominant allele (B)
- Homozygous Recessive: bb = Both recessive alleles
28
Homozygous vs Heterozygous
- A heterozygous genotype stands in contrast with a homozygous genotype, where an individual inherits identical alleles of a particular gene from each parent.
29
Why does Mitosis occur?
- Growth: Cell division is key to life; for bodies to grow and develop we must produce new cells and allow for death of old cells
- Repair: Cell division and repair (healing and regeneration); our body is continually making repairs e.g cuts and broken bones, bodies make new blood cells every 120 days.
- Reproduction: Cell division plays central role in asexual reproduction
30
Mitosis
- Occurs in body cells/somatic cells
- Process where single cell divides to produce two genetically identical daughter cells (clones); daughter cells are identical to parent cell
- Body cells that are produced during mitosis are diploid (46 chromosomes); (2N, contain two sets of chromosomes
- PMAT
- Prophase: chromosomes visible; nuclear membrane disappears; spindle fibres extend from centrioles and connect to the chromosomes
- Metaphase: chromosomes line up along the equator
- Anaphase: chromosomes split in half and are pulled to opposite side of poles as spindle fibres shorten
- Telophase: two new cells are ready to separate from one another; nucleus starts to reform; two identical cells produced
31
Meiosis
- Cell division that occurs in reproductive organs to produce sex cells/gametes
- Produces sperm and egg cells
- Forms 4 daughter cells
- Produces genetically unique sex cells with only 23 chromosomes (haploid)
- Each cell (sperm/egg) has 23 chromosomes (haploid) Haploid cells (n) have one set of chromosomes
32
Phases of Meiosis
1. Metaphase I = Replicated chromosomes form homologous pairs, attached to spindle fibres and lined up in the middle
2. Anaphase I - One replicated chromosome of each pair moves to each pole
3. Telophase I - Two cells are formed, each with one replicated chromosome
4. Metaphase II Chromosomes line up on the equator attached to spindle fibres
5. Anaphase II - Chromatids separate and move to poles
6. Telophase II - Four cells result with one copy of each chromosome, they are haploid gametes
33
Mutations
- Sometimes mistakes occur during meiosis when the sex cells are produced and information passed onto next generation is changed
- E.g If chromatids fail to separate during meiosis, child will be born with extra chromosome or part of a chromosome: chromosomal abnormality
- Mutations may arise spontaneously or result from damage to a strand of DNA, radiation and some chemicals and viruses can cause mutation
- Mutations do not necessarily cause a problem; can create a different or even better version of a protein; mutations add to diversity of organisms
34
Causes of mutations
- Agents that cause mutation are called mutagens; both chemical and physical agents
- Mutation may cause breaks in DNA, replace a normal base, form abnormal bonds between bases, or activate genes that cause the cell to grow out of control
Common agents of mutations - radiation: x-rays or UV rays, chemical: cigarette smoke, asbestos, arsenic, biological: hepatitis B virus
35
Nucleotides
- Make up DNA
- An organic molecule with a basic composition of a nitrogenous base, pentose sugar and phosphate
36
Amino Acids
Make up proteins. Proteins form living cells, cells make up tissues, and tissues make organs which combine to make living organisms.
37
Why is DNA known as a 'blueprint of life'?
DNA is a plan for building a particular living thing, or organism. It provides a set of instructions for making proteins, which are the building blocks of cells. Cells are the building blocks of living things. So DNA is essential for determining how a living thing develops, what parts it has, and how it behaves.
38
Co-dominance
Condition where the phenotypes of both alleles of a particular gene are expressed simultaneously in a heterozygote, e.g. striped and spotted, in different spots
Two parent phenotypes are expressed together in their offspring. The two alleles neither act as dominant or recessive over the other. A hybrid will not result in the formation of a new phenotype.
39
In-complete dominance
Where neither trait is dominant over the other, so the organism expresses both alleles, blending the two and creating a new genotype [e.g red (dominant) + white (dominant) = pink]
Two parents blend together to create a new phenotype for their offspring. One allele is not completely dominant over the other. A hybrid will always result in a new phenotype.
40
Mitosis and Meiosis cells produced
41
Karyotype
An individual's complete set of chromosomes
42
DNA size
