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genetics Flashcards

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1
Q

what is genetics?

A

the study of heredity and natural variation.

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2
Q

heredity?

A

how traits are passed from parents to their children.

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3
Q

how does each person become unique?

A
  • we inherit one set of chromosomes from each parent (how we are similar to them)
  • because we get different combinations of genes and because small differences (natural variation) which makes each person unique
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4
Q

natural variation?

A

result of inherited characteristics and the environment. Reason individuals look different.

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5
Q

Explain how traits are passed from parents to offspring

A

Traits are passed through genes. Each parent contributes one allele for each gene through their gametes (egg and sperm). The combination of alleles determines the offspring’s traits.

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6
Q

DNA?

A

chemical molecule that carries genetic information.

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7
Q

Genes?

A

sections of DNA that act as instructions for specific traits or proteins.

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8
Q

Chromosomes?

A

long, tightly coiled strands of DNA that contain many genes.

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9
Q

Relationship between DNA, genes and chromosomes

A

DNA makes up genes, and genes are found on chromosomes.

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10
Q

Describe how environment and genetics both influence phenotype

A

Genes provide the instructions for a trait, and the environment affects how strongly or how those instructions are expressed, together determining the phenotype.

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11
Q

structure of DNA?

A
  • double helix
  • sugar-phosphate backbone
  • bases (rungs of the ladder)
  • complementary strands
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12
Q

Identify the three parts of a nucleotide

A

: Phosphate, Deoxyribose sugar, Nitrogenous base

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13
Q

bases (rungs of the ladder)?

A

the rungs are made of pairs of nitrogen bases
- adenine (A)
- thymine (T)
- cytosine (C)
- guanine (G)

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14
Q

how do the nitrogen bases pair?

A

they pair in a specific way called base pairing
A pairs with T
C pairs with G

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15
Q

How DNA stores genetic information

A

The sequence of bases (A, T, C, G) forms a code. The order determines which protein is made.

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16
Q

how does DNA make protein?

A

DNA base sequence → determines amino acid sequence → amino acids join to form a protein → proteins determine traits.

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17
Q

what are chromosomes?

A

a package of DNA that carires genes

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18
Q

what do chromosomes contain?

A

instructions for traits and how the body works

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19
Q

where are chromosomes found?

A

in the nucleus of a cell

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20
Q

how many chromosomes are there in humans body cells and sex cells?

A

humans have 46 chromosomes in body cells (23 pairs) and 23 sec cells

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21
Q

diploid (2n) meaning?

A

any cell that has 2 sets of chromosomes. e.g humans 46 in body cells

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22
Q

haploid (n) meaning?

A

any cell that has 1 set of chromosomes e.g humans 23 in sex cells

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23
Q

chromosome structures: Sister chromatids

A

Sister chromatids: Identical copies of a chromosome.

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24
Q

chromosomes structures; Centromere

A

Centromere: The point where sister chromatids are joined.

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25
what are karyotypes?
picture of all chromosomes in a cell, arranged in pairs smallest to largest
26
purpose of karyotypes?
- to see the number of chromosomes - check for abnormalities
27
humans and karyotypes?
- normal karyotype = 46 chromosomes in pairs
28
trisomy
xtra chromosome (e.g., Down syndrome = Trisomy 21)
29
Monosomy
Missing chromosome
30
what is reproduction?
reproduction is the biological process by which living organisms produce offspring. It ensures the continuation of a species from one generation to the next.
31
asexual reproduction
- only one parent - produces offspring that are genetically identical to parent
32
sexual reproduction
- involves two parents - combination of their genetic material - offspring genetically different to parents
33
(cell division) - Mitosis
- type of asexual cell division as mitosis produces offspring without needing another parent - allows a single cell to produce 2 genetically identical daughter cells - how cells make exact copies of themselves
34
2 purposes of mitosis
1. growth - helps organisms grow by increasing the number of cells 2. repair - replaces damaged or dead cells (like skin or blood cells)
35
3 stages of the cells cycle
1. interphase 2. mitosis 3. cytokinesis
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1st stage of cell cycle interphase
cell grows and DNA is replicated Nucleus visible, chromosomes not yet distinct
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2nd stage of cell cycle mitosis 4 things
prophase metaphase anaphase telophase
38
2nd stage of cell cycle prophase meaning
chromosomes become visible; the nuclear membrane starts to break down
39
2nd stage of cell cycle metaphase
chromosomes line up in the centre of the cell
40
2nd stage of cell cycle anaphase
chromosomes are pulled apart to opposite sides of the cell
41
2nd stage of cell cycle telophase
nuclear membranes form around each set of chromosomes Two nuclei forming, chromosomes decondensing
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3rd stage of cell cycle cytokinesis
the cell splits into 2 identical daughter cells
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Chromosome number before & after mitosis
Before: 46 After: 46 (no change) cells genetically identical
44
Why daughter cells are identical
DNA is copied exactly before division, and chromatids separate evenly.
45
Why meiosis is reduction division
It reduces chromosome number from diploid (2n) to haploid (n).
46
Explain why meiosis produces haploid cells
Meiosis produces haploid cells because it separates chromosome pairs, so each new cell gets only one set instead of two.
47
Why gametes must be haploid
So when fertilisation occurs, the zygote has the correct diploid number (46).
48
Two divisions
Meiosis I separates chromosome pairs. Meiosis II separates sister chromatids.
49
crossing over meiosis
when matching chromosomes swap sections of DNA during Prophase I of meiosis, creating new combinations of genes.
50
meiosis independent assortment
Random arrangement of chromosome pairs during Metaphase I.
51
how meiosis increases variation
Crossing over Independent assortment Random fertilisation
52
comparison of mitosis and meiosis - purpose
mitosis - growth, repair, asexual reproduction meiosis - production of gametes (sex cells) for sexual reproduction
53
comparison of mitosis and meiosis - number of divisions
mitosis - 1 division meiosis - 2 divisions (Meiosis I and Meiosis II)
54
comparison of mitosis and meiosis - number of daughter cells
mitosis - 2 cells meiosis - 4 cells
55
comparison of mitosis and meiosis - genetic similarity
mitosis - genetically identical to parent cell and each other meiosis - genetically different from parent cell and from each other
56
comparison of mitosis and meiosis - chromosome number
mitosis - maintains diploid number (2n -> 2n) meiosis - halves chromosome number (2n -> n)
57
comparison of mitosis and meiosis - occurs in
mitosis - somatic (body) cells meiosis - reproductive organs (ovaries/testes)
58
comparison of mitosis and meiosis - crossing over
mitosis - does not occur meiosis - occurs to increase genetic variation
59
comparison of mitosis and meiosis - independent assortment
mitosis - does not occur meiosis - occurs to increase variation
60
comparison of mitosis and meiosis - role in variation
mitosis - no new genetic variation meiosis - creates genetic variation in offspring
61
comparison of mitosis and meiosis - type of reproduction
mitosis - asexual meiosis - sexual
62
inheritance
passing traits from parents to offspring
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allele
different versions of the same gene e.g alleles for brown (B) or blue eyes (b)
64
genotype
the genetic makeup of an organism (e.g BB Bb tt)
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phenotype
the physical trait shown (e.g brown eyes)
66
dominant allele
an allele that is expressed (shows its effect) when one copy is present (A)
67
recessive allele
an allele expressed only when two copies are present (a)
68
homozygous
having two identical alleles (BB or bb)
69
punnett square
a diagram used to predict genetic outcomes
70
heterozygous
having two different alleles (Bb)
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heterozygous x heterozygous
1:2:1 ratio
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Dominant alleles mask recessive
If a dominant allele is present, it determines the phenotype.
73
Why recessive traits skip generations
they require two copies of the recessive allele (homozygous recessive) to be expressed
74
Why recessive traits reappear
because they can be "hidden" in carriers (heterozygotes) who possess one dominant and one recessive allele
75
what is genetic testing
Testing DNA to identify genetic conditions or risks.
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6 reasons why genetic testing is done
Diagnostic – Confirms a condition Carrier – Identifies carriers Predictive – Shows future risk Prenatal – Before birth Newborn screening – At birth Preimplantation – IVF embryo testing
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benefits of genetic testing
Early treatment Informed decisions Family planning
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limitations and risk of genetic testing
Emotional stress Privacy concerns False positives/negatives Ethical issues
79
5 core principles of bioethical principles
1. beneficence - "do good" 2. non - maleficence - "do not harm" 3. respect (autonomy) 4. justice - "fairness" 5. integrity
80
1. beneficence - "do good"
- healthcare professionals should act to benefit the patient
81
2. non - maleficence - "do not harm"
- avoid causing physical, emotional, or social harm
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4. justice - "fairness"
- everyone should be treated equally and given equal access to healthcare
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3. respect (autonomy)
- people have the right to make their own informed decisions
84
5. integrity
- act honestly, follow ethical standards, and uphold professional responsibilities
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VARIATION
Differences between individuals, eg different hair colour, eye colour, weight, height
86
ENVIRONMENT
Factors that affect the phenotype/characteristics of an organism that are not passed on through genetic material
87
GENOME
A genome is all the genetic information of an organism or cell required for the organism to function, grow, and develop. It consists of nucleotide sequences of DNA.
88
MUTANT
Any phenotype that is not the most common for a particular trait in a population.
89
NUCLEOTIDE
A monomer/sub unit of DNA that made up of a phosphate group, a deoxyribose sugar group and a nitrogenous base.
90
DOUBLE HELIX
The way two complementary strands of DNA are arranged, joined together by HYDROGEN BONDS between complementary bases eg A=T and G-=C (3 hydrogen bonds)
91
HYDROGEN BOND
Link together adjacent nucleotides in a double strand of DNA.
92
HOMOLOGOUS CHROMOSOMES
‘Paired’ chromosomes ie. the same genes occur in the same positions. Of the 23 pairs of homologous chromosomes, the last pair is the sex chromosome pair; females XX, males XY
93
AUTOSOME
All of the chromosomes other than the sex chromosomes, eg most human cells have 44 autosomes (in 22 pairs)
94
MUTATION
Any change in the hereditary material (ie a change to the coding sequence of the DNA., such as a T replacing an A on one of the strands)
95
ZYGOTE
A fertilized egg. This contains the chromosomes from both the male and female gametes (sex cells) and so have 46 chromosomes (in humans).
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