B13 Reproduction Flashcards
How many chromosomes are in a body cell nucleus?
46 Chromosomes
What are chromosomes made of?
DNA and Proteins
What do each chromosomes have?
Two sister chromatics
Why is DNA negatively charged?
It contains PO4^-3 (phosphate ions) which are negative.
What does DNA stand for?
Deoxyribonucleic Acid
What is DNA?
A double stranded molecule with a helix structure which is a polymer of nucleotides
What does each nucleotide consist of?
- A nitrogen base
- A sugar group
- A phosphate group
What are the four types of nitrogen bases?
- A
- T
- C
- G
How are the complementary nitrogen bases formed?
Hydrogen bonds are made inbetween the complementary bases.
What are the complementary nitrogen bases?
- A=T
- C≡G
What are between two strands of DNA?
Sugar phosphate back bone and complementary bases
What are the two types of protien synthesis?
Translation and Transcription
What occurs during transcription?
- Unzipping of DNA
- Free nucleotides within the nucleus bind with their complementary bases (T is replaced by U)
- Nucleotides joined together to form a single stranded molecule called M-RNA
- M-RNA leaves the nucleus through nucleo-cords
What is unzipping of DNA?
Hydrogen bonds between complementary bases are broken down within the section of gene.
What occurs during translation?
- M-RNA molecules bind with a ribosome in the cytoplasm
- There are t-RNA molecules in the cytoplasm with complementary anticotons and amino acids
- t-RNA transfers amino acids to ribosomes so that amino acids can join together to form a protien
What is a triplet-codon?
Three bases on M-RNA are called a triplet-codon, which codes for one specfic amino acid
What is an anti-codon?
Triplet in the t-RNA
Why is the function of a protein determined by order of bases in DNA?
- Function of a protein is affected by a structure of protein
- Structure of the protein is affected by order of amino acids
- Order of amino acids is affected by order of triplet coton on M-RNA
- Order of cotons is affected by base sequence in DNA
What are the differences between Asexual and Sexual reproduction?
- Asexual is only on parent;Sexual requires two parents
- Asexual offspring are genetically identical; Sexual offspring have genetic variation
- Asexual requires less energy; Sexual require more energy
What are the advantages of asexual reproduction?
- Quicker
- Less energy
- Offsprings have desired characteristics can be produced
What are the disadvantages of asexual reproduction?
- No genetic variation among organisms which means they’ll be susceptible to new pathogenic diseases
What are the advantages of sexual reproduction?
Variation amongst offsprings which means organisms can adapt to chaning conditions
What are the disadvantages of sexual reproduction?
- Requires two parents
- More energy
- Long
How can plants asexual produce in plant cuttings?
1) Cut a healthy branch in the stem
2) Add rooting powder to simulate root formation
3) Add soil and nutrients
What is mutation?
A random change in nucleotide sequence in a gene
What are the three types of mutations in a gene?
- Addition
- Deletion
- Substitution
What happens during addition mutation?
- additional base is added in between two nucleotides
- this will change the sequence of codons on m-RNA and the order of amino acids
What is a genome?
A genome is the entire genetic material in an organism
How does the understanding of the human genome help those with inherited disorders?
Helps identify risk factors for certain patients to help them improve or change their lifestyle
How does the understanding the human genome help us understand human evolution and history?
Understanding the human genome links patterns in peoples DNA so scientists can trace migration patters and early ancestors.
What is a diploid cell?
A cell that contains 46 chromosomes (23 pairs)
What is a haploid cell?
A cell that contains one set of chromosomes (23)
What is the male gamete in animals?
Sperm
What is the female gamete in animals?
Egg
What is the male gamete in plants?
Pollen
What is the female gamete in plants?
Egg
How many rounds of cell division occur in the process of meiosis?
2 rounds of cell division
How many cells are produced in meiosis?
4 gametes are produced
Describe how a zygote develops into an embryo and then a functional organism.
The zygote will divide by mitosis to form an embryo.
Cells continue to divide and begin to differentiate into specialised cells that form tissues and perform different functions within the organism.
What is an allele?
Different forms of the same gene.
What is phenotype?
Observable characteristics that are determined by the genotype.
What type of chromosomes do men have?
XY
What type of chromosomes do women have?
XX
Explain how it is possible for an offspring to have cystic fibrosis when neither of their parents have the disease?
Cystic fibrosis is caused by a recessive allele.
Both of the parents must be heterozygous for the allele / carriers of the disease.
What are the advantages of screening IVF embryos for genetic diseases?
- Prevents suffering.
- Saves money in long term.
- protected by laws to stop process being abused.
What are the disadvantages of screening IVF embryos for genetic diseases?
- Implies that people with disorders are undesirable which is unfair/incorrect.
- Screening can be expensive.
- People may take advantage of screening and pick embryos based of other desired characteristics.
- Opposed by people who believe embryos are potential new lives and don’t agree with defective embryos being destroyed.
Which pair of the 23 chromosomes determines the sex?
Last pair
What is Antenatal testing?
Antenatal testing is used to analyse an individual’s DNA or chromosomes before they are born
Who is Antenatal testing usually offered to?
To couples who may have an increased risk of producing a baby with an inherited disorder, but it can’t detect all the risks of inherited disorders.
What is Neonatal testing (new born blood spot test)?
A test analysing a sample of blood that is taken from pricking a baby’s heel. It detects genetic disorders in order to treat them early.
When in a person’s life can a genetic test be taken?
At any point in their life
What is Pre-implantation genetic diagnosis PGD)?
Pre-implantation genetic diagnosis is used on embryos before implantation. Once the embryos have reached the eight-cell stage, one cell is removed.
The cells are tested for the disorder-causing alleles. Embryos that don’t contain the disorder allele are implanted into the uterus.
What are the limitations of genetic testing?
- False Positives
- False Negatives
- Gene Therapy
What is gene therapy?
Gene therapy involves inserting copies of a normal allele into the chromosomes of an individual who carries a faulty allele (however it’s not always successful)
What are the steps of gene therapy?
1) Identify the gene involved in the genetic disorder
2) Restriction enzymes cut out the normal allele
3) Many copies of the allele are made
4) Copies of the normal working allele are put into the cells of a person who has the genetic disorder due to a mutated or faulty copy of an allele
What are problems in the process of gene therapy?
- The alleles may not go into every target cell, which are cells that need the new non-faulty cell
- The alleles may be inserted into the chromosomes in random places, rather than in the required position, so they do not work properly
- Some treated cells may be replaced naturally by the patient’s own untreated cells, as cells are frequently replaced through the process of mitosis during growth and repair
What are different alternatives to gene therapy?
- using nose sprays, which allow a patient to introduce the working allele up their nose and it will be taken into their body and incorporated
- using cold viruses that are modified to carry the allele - the viruses go into the cells and infect them
- the direct injection of DNA
Why may gene therapy have ethical concerns?
People disagree with gene alteration in people, as they believe it is unnatural.
Why may people agree with gene therapy?
-It prevents unnecessary suffering in affected individuals.
- Gene therapy only affects the individual involved in the process and not any future generations who would be likely to inherit similar diseases.
