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Science 2022 Sem2 > DNA and Genetics 2022 > Flashcards

DNA and Genetics 2022 Flashcards

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Biology 101 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
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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
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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
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4
Q

Examples of key organelles

A
  • Mitochondria
  • Plastids
  • Vacuoles
  • Chloroplast (plant)
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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
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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
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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.
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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
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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.
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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
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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
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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
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13
Q

Number of human chromosomes

A

Humans = 46 Chromosomes (somatic/body cells)

You get 23 chromosomes from each parents gametes.

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14
Q

What are non sex chromosomes called?

A
  • Autosomes
  • Non-sex chromosomes: 44 chromosomes/22 pairs
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15
Q

Sex chromosomes

A
  • 23rd pair of chromosomes: sex chromosomes
  • Female: XX
  • Male: XY
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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
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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
Q

Dominant Alleles

A
  • Dominant alleles mask the effect of the other allele. (Shown as the uppercase letter)
26
Q

Recessive alleles

A
  • Hidden or masked by the dominant allele
  • Although it is not physically expressed, it is still there
27
Q

Types of alleles

A
  • 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
Q

Homozygous vs Heterozygous

A
  • A heterozygous genotype stands in contrast with a homozygous genotype, where an individual inherits identical alleles of a particular gene from each parent.
29
Q

Why does Mitosis occur?

A
  • 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
Q

Mitosis

A
  • 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
Q

Meiosis

A
  • 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
Q

Phases of Meiosis

A
  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
Q

Mutations

A
  • 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
Q

Causes of mutations

A
  • 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
Q

Nucleotides

A
  • Make up DNA
  • An organic molecule with a basic composition of a nitrogenous base, pentose sugar and phosphate
36
Q

Amino Acids

A

Make up proteins. Proteins form living cells, cells make up tissues, and tissues make organs which combine to make living organisms.

37
Q

Why is DNA known as a ‘blueprint of life’?

A

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
Q

Co-dominance

A

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
Q

In-complete dominance

A

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
Q

Mitosis and Meiosis cells produced

A
41
Q

Karyotype

A

An individual’s complete set of chromosomes

42
Q

DNA size

A

Science 2022 Sem2 (3 decks)

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