Chapter 3 Flashcards
Advantages and disadvantages of asexual reproduction
A- Rapid populating, no need for a mate and can exploit suitable habitat quickly
D-no variation within population, disease may effect all the individuals in a population, species may only be suited to one habitat
Advantages and disadvantages of sexual reproduction
A- introduces variation, species can adapt to new environments and diseases is less likely to affect all In a population.
D-time and energy needed to find a mate, not possible for an isolated individual
What happens in meiosis and what its used for
Same steps as mitosis but 2 homologous chromosomes separate to create 2 daughter nuclei. The 2 daughter nuclei divide, chromosomes the are themselves separated. It creates 4 genetically different haploid gametes for sexual reproduction
Describe DNA
A polymer made up of 2 strands coiled to form a double helix, the strands are linked by a series of complementary base pairs joined together by hydrogen bonds. Nucleotides that consist of a sugar and phosphate group with 1 of the 4 different bases attached to the sugar/
What is a genome
An organisms complete set of DNA or genetic material present in a cell or organism.
How can DNA be extracted from fruit
Salt water mixed with soap with the mashed up fruit. Leave mixture for 15 mins at 60*. Then filter the mixture and pour iced ethanol on to the filtrate. The DNA floats to the surface.
What do the order of bases in a section of DNA do?
Decide the order of amino acids in the protein and that these fold to produce specifically shaped proteins such as enzymes
What are amino acids
When bonded together to make long chains called proteins which have influence on many of our bodily functions eg- giving cells structure and repairing tissue.
Letters in DNA and which ones match?
A and T
C and G
What is protein synthesis
Creation of a new protein.
Each protein is made up of large numbers of amino acid molecules. Each triplet of bases codes for one particular amino acid. Amino acids are made in the number and order dictated by the numbers and orders of base triplets.
Amino acid molecules join together in a long chain to make a protein molecule. The number and sequence of amino acids determines which protein results.
Describe the stages in transcription
x1-In the nucleus DNA is split in half by helicase
2-Strands created are the non coding and coding strand
3-RNA polymerase joins to the non coding strand of DNA at the beginning of the gene
4-Complementary bases attach to the strand being copied- C-G and U-A (uracil replaces Thymine)
5-RNA then copies DNA into an exact copy of RNA called mRNA
Describe the stages in translation
1-The mRNA leaves through the nucleus pores and u to the cytoplasm where it joins to ribosomes
2- tRNA molecules transport specific amino acids to the ribosome
3-each mRNA codon codes for a specific amino acid
4-anti codons and codons match up and form complimentary base pairs
5-a polypeptide chain is formed - PROTEIN
How can genetic variants in the non- coding DNA of a gene affect phenotype?
Influencing the binding of RNA polymerase and altering the quantity of the protein produced
How can genetic variants in the coding DNA of a gene affect phenotype?
Altering the sequence of amino acid and therefore the activity of the protein produced.
Describe the work of Mendel
Gregor mendel cross bred distinctively different plants and discovered that there are dominant and recessive traits passed on. He also discovered that traits from the parents were given to offspring
Explain why there are differences in the inherited characteristics
Alleles may be dominant or recessive, those dominant will be passed down and those of 2 recessive will be passed down. There are different possible outcomes therefore can cause differences, mutations can also cause differences
What is a chromosome
Rod shaped bodies found in the nucleus of cells that contains genetic information
What is a gene
A short section of DNA, each gene codes for a specific protein by specifying the order in which amino acids must be joined together- they code for specific characteristics of phenotypic traits
What is an allele
Different forms of the same gene that can be dominant or recessive.
What is meant by dominant
A dominant allele always shows, even if the individual only has one copy of the allele. For example, the allele for brown eyes is dominant. You only need one copy of the allele to have brown eyes (and two copies will still give you brown eyes).
What is meant by recessive
A recessive allele only shows if the individual has two copies of the recessive allele. For example, the allele for blue eyes is recessive. You need two copies of the allele to have blue eyes.
What is hetrozygous
A certain gene carrying two different alleles
What is homozygous
A certain gene carrying two copies of the same alleles
What is a genotype and phenotype
The genotype of an organism is defined as the total sum of all the genes. The phenotype of a organism is the observable physical characteristics of an organism.
What is a gamete
A sex cell eg sperm and egg
What is a zygote
The cell formed from fertilization which will then go on to form an embryo
How is the sex of an off spring determined
A chromosome from a sperm cell, either X or Y,fuses with the X chromosome in the egg cell.
If the X fuses it’s a girl (XX)
If the Y fuses it’s a boy (XY)
How are sex linked genetic disorders inherited
Dominant/Recessive genes
eg Hemophilia and colour blindness
What are phenotypic features a result of
Multiple genes rather than single gene inheritance
What are the causes of variation that influence phenotype
Environmental-Differences in the environment
Acquired / adapted characteristics or mutations in`genes- inherited
What is the outcome of the human genome project and potential applications within medicine
Mapping all of the genes of a human genome
- gives detailed information about chromosomes
- 3.2 billion bases molecules make up the DNA code
- further scientific knowledge and development
- help us learn more about genetic disorders
What causes extensive genetic variation within a population of a species
Sexual reproduction and Mutations- Mutations produce random changes in an organisms genetic code, this causes a different protein to be produced or none.
Why don’t most genetic mutations have no effect on the phenotype
A mutation could occur in a stretch of DNA with no function or not affecting amino acid sequence of protein
Where are proteins made
Ribosomes - they strung together long chains of amino acids
What are the names of the 4 bases of DNA
Adenine
Cytosine
Thymine
Guanine
Characteristics controlled by multiple genes
ABO blood groups
Hair colour
Hair texture
Eye colour
Continuous and discontinuous variation
Continuous is when there is no limit on the value that can occur in the population e.g.- height, weight and finger length
Discontinuous is when there are distinct groups and it is limited e.g. Blood group, tongue rolling and finger prints
How can Mutations occur?
Caused by environmental factors such as ultraviolet radiation
Hereditary mutations
DNA fails to copy accurately- a change in the sequence.
What is a mutation
A change in the DNA
How is the order of amino acids in protein determined
Each triplet of bases code for one particular amino acids, they are dictated by the number and order of base triplets
What are the 2 stages of protein synthesis and give a brief description
1st stage takes place in the nucleus and is called transcription
2nd stage takes place in the cytoplasm and is called translation
