Reprpduction And Inheritance Flashcards
Explain the process of translation
1)the mrna strand travels through the cytoplasm and attaches to the ribosome
2)tRNA molecules, which have a specific anticodon on them, pair with the complementary triplet (codon) on the mrna
3)tRNA molecules also have a site in them where amino acids can attach to, so the tRNA molecules bring with it it’s specific amino acid
4)the ribosome moves across the mrna strand, and another tRNA molecule moves in, brining with it it’s specific amino acid
5)used tRNA molecules leave the ribosome to collect another amino acid
6) the process continues until a stop codon is reached on the man’s strand
7) and so a polypeptide chain, which consists of a chain of many amino acids bonded by peptide bonds is formed. This then folds into shape to produce a specific protein.
What is a gene
A section of dna that codes for a particular protein
Describe the structure of dna
A nucleic acid, a chemical.
Which is a polymer, made up of small units called nucleotides
Each nucleotide is made up of a sugar, phosphate and a base,
And many nucleotides join together to form 2 strands cooled together, which is called a double helix structure
What is a karyotype
A diagram, which shows a full set of human chromosomes
Every nucleotide has the same… and…. But different……
Sugar, and phosphate group,
bases
Stats the exact names of the parts of a dna nucleotide
(Pentose) Sugar deoxyribose
Phosphate
Basée (ATGC)
Give three examples of proteins
-structural proteins like keratin,
-enzymes
-hormones
State three differences between DNA and RNA
Dna consists of two strands whereas rna consist of 1 strand
Dna contains the sugar deoxyribose, but rna consists of the sugar ribose
Dna contains the bases guanine, cytosine, adenine, thymine, BUT RNA consists of the bases guanine, cytosine, adenine, uracil
What is a genome
The entire dna that makes up an organism
Explain the process of mitosis
Interphase: -Before mitosis, chromosomes are replicated to form exact copies of themselves, called sister chromatids, forming the x shape chromosome
Prophase: -the chromatids condense and become more visible
-and each cheomome is joined by a centromere.
-the nuclear membrane also breaks down
Metaphase:-the chromosomes line up on top of each other at the equator, and spindle fibers attach at the centromere
Anaphase: the spindle fibers shorten and pull apart the sister chromatids to opposite poles of the cell
-the chromomes have separated now to form a full set of homologous chromosomes for 2 daughter cells
Téléphase: nucleus forms at the poles of the cell as the cytoplasm divides,
- with a full set of 46 chromosomes, and so two daughter nuclei have been formed
-which are identical to the parent
Explain the process of meiosis
1)chromosomes replicate themselves and line up at the equator in random order
2)during the first division, chromosomes are pulled apart by spindle fibers, where one chromosome from each homologous park will go into a different daughter cell.
-two diploid daughter cells will be formed, each having 46 chromosomes
3)-in the second division, the chromosomes line up again at the equator and are pulled apart by spindle fibres
-the cells are divided again into four daughter cells, where now each cell is haploid and so contains only 23 chromosomes
4)all the gametes will be genetically different to each other, due to the random shuffling of maternal and paternal chromosomes in each cell, so they have different combinations of alleles
How does….. being about genetic variation
Meosis
Because there is a random shuffling of maternal and paternal chromomes in each gamete
Therefore the offspring will have a different combination of alleles
Give three uses of mitosis
-produces all cells of the body apart from gametes
-repairs and replaces damaged tissues
-important for asexual reproduction because it produces offspring which are genetically identical to the parent
Give two uses of meosis
-produces gametes
-important for bringing about genetic variation among offspring
Give four differences between mitosis and meiosis
Mitosis results in produces diploid daughter cells, but meosis haploid daughter cells
Mitosis produces body cells, meosis produces gametes
Mitosis produces 1 daughter cells, so 2 divisions, meosis produces 4 daughter cells so 2 division
Mitosis does not result in genetic variation, meosis does result in genetic variation
Explain the process of transcription
1)dna is too large to leave the nucleus, therefore help case enzyme “unzips” and “unwinds” the two strands of dna , as the hydrogen bonds between the complimentary base pairs break
2)the template strand of dna is exposed, which will form the framework for mrna to form
3)rna polymerase attaches to the dna strand and moves across it
4) free rna nucleotides base pair with the complimentary dna bases, to form a strand of mrna
5)mrna is now an exact copy of dna, (except that thymine is replaced with uracil) and so leaves the nucleus through the cytoplasm and attaches to a ribosome
During transcription, how is helicase enzyme able to unzip and unwind the two strands of dna
Because it breaks the hydrogen bonds between the complimentary base pairs
In rna, uracil replaces….
Thymine
Phenotype meaning
Observable characteristics of an organism
Give the six stages needed to be included inside a monohybrid cross
1)parents phenotype
parents genotype
Parents gametes
Punnet square
Offspring genotype
Offspring phenotype
Explain the difference between monohybrid inheritance and polygenic inheritance
Monohybrid is inheritance of characteristics, controlled only by a single gene
Polygenic inheritance is inheritance of characteristics, controlled by more than one gene, therefore it can result in many different phenotypes
Inheritance of sex depends upon….
The sperm cell from the male has , because only he Carrie’s the xy chromosome
Every time offspring is produced, there is a …. Chance of it being girl and… chance of it being boy
50%
Give an example of codominance, and state which alleles are dominant over which
Blood group
I^A and I^B are dominant over I^O
Whereas I^A and I^B are codominant
What is codominace
When neither allele is dominant over the other, so both alleles within the genotype are expressed
What is a genotype
The combination of alleles that control a characteristic
Explain how there is genetic variation in human offspring
Because firstly, each gamete has a different variation of maternal and paternal chromosomes due to meosis, therefore they each have a different combination of alleles
And because the fusion of the sperm and egg cell are random (any one sperm can fuse with any one egg)
State the three types of ways genetic variation can occur and give examples
Genetic- eye colour
Environmental -mass because of diet
Both - height
What is a mutation
A change in the dna base sequence,
Which is a rare and random change and can be inherited
Describe two ways in which the risk of mutations can increase
Being exposed to gamme or x rays, because these are ionizing radiation, which can damage base sequences
Carcinogens
Explain how a mutation can change a phenotype
1)mutation occurs and so the order of bases in a gene is changed
2)because each triplet codes for a specific amino acid, the sequence of amino acids changes
3)and because a particular amino acid codes for a particular protein, the shape will change and so it will code for an the entire different protein
Express two ways in which mutations can occur which is normal
Alleles are the result of a mutation, because they are different forms of the same gene
Happens spontaneously in cells when dna is duplicated during mitosis
Explain why most mutations have no effect on a phenotype
Because most dna is non coding, so doesn’t even code for a specific protein
What is non coding dna
One that doesn’t code for any particular protein
And can control whether a gene is expressed or not express
Give examples of two ways that mutations can be harmful
They can damage the shape of the active site of an enzyme, so that it can no longer form enzyme substrate complexes
In the disease called sickle cell anemia, where the shape of haemoglobin is altered, so red blood cells become stiff and sticky, so it can block narrow blood vessels and so prevent the flow of blood
Explain Darwin’s theory of evolution
That within a species there is variation
This variation means that there is competition between offspring, so those most suited for the environment will have a higher chance of surivival,
Therefore those most well adapted with the most advantageous phenotypes will survive and reproduce, passing on their alleles to their offspring, whilst the others will die out
This process continues over generations until the frequency of those with the advantageous phenotype increases and so is more common
Evolution defintion
The gradual change in a populations inherited characteristics over time due to natural selection
Natural selection defintion
The process where by individuals who are better adapted to the environment survive and reproduce
What is speciation and how does it happen
Process where by a population becomes so different from each other that they can no longer interbreed
Happens When a species has been divided by a physical barrier such as a river, and so there are different environments
So these different selection pressures cause the species on each side to adapt accordingly by natural selection, and so overtime the species will evolve and these most advantageous phenotypes will be most frequent
Give three ways in which antibiotic resistance can be controlled
Should not be prescribed for viral infections
Shouldn’t be prescribed for minor infections that the immune system is capable of handling
Patients should ensure that the course is finished, so that there are no bacteria left to mutate
Explain how antibiotic resistance occurs
Within bacteria, there is variation, because random mutations occur all the time
One of these mutations however may be a mutation that is antibiotic resistant
When exposed to an antibiotic, those without this phenotype will die out, whereas the antibiotic resistant ones will not
Therefore there is less completion for survival for the resistant strains
So they pass on their alleles to their offspring and begin to reproduce rapidly
Overtime, the entire population becomes antibiotic because the frequency of this phenotype has increased and so it is hard to control
Give two advantages of sexual reproduction and one disadvantage
There is variation within offspring, which is advantageous because species can better adapt to environmental changes and survive
Less genetic variation means more susceptible to disease
Disadvantage:
Difficult for isolated members to mate
Give two advantages and two disadvantges of asexual reproduction
Advantages:
-only one parent required
-population can be increased rapidly
Disadvantages:
-offspring genetically identical so can less likely adapt to changes and so survive
-less genetic variation means entire population more susceptible to disease
Give an example of the only time where a dominant gene may not be passed on
If the is spring has two heterozygous parents
(Because do a punnet square, and you get BB Bb Bb bb
So two recessive alleles will also be present)
By looking at a family pedigree chart, how would you be able to tell if a disease was carried on by a recessive allele
Is recessive, than allele will be present by skipping generations
And there will always be a carrier present
Describe three differences between natural selection and selective breeding
Natural selection is much slower process
In selective breeding the parents are chosen
There is no completion and survival of the fittest in selective breeding
What does it mean if an organism is pure breeding
It means that it is homozygous for that particular characteristic
Who is sex inheritance determined on and why
The male
Because his sperm can have either the x or the Y chromosome
Explain how the number of chromosomes in the offspring are maintained, although the gametes only contain half the number
This is because gametes are made by meosis, so contain 23 chromosomes each, haploid number
But at fertilisation, the egg and speed cell fuse together,
So diploid cells are formed which contain a full set of chromosomes
Dominant allele meaning
Type of allele always present in the phenotype
Even if only one copy is present in the genotype
Even if a genetic disease is dominant, explain why the number of people who have the disease are still few
Because they are unlikely to reproduce,
Therefore the allele is rare
Give three functions of testosterone
Develops male secondary characteristics eg oubic hair
Creates a sex drive
Produces sperm
