B13 - Reproduction Flashcards
What are alleles?
Different forms of the same gene, sometimes referred to as variants
What is asexual reproduction?
involves only 1 individual and the offspring is identical to the parent. There is no fusion of gametes or mixing of genetic information
What are bases (DNA)?
Nitrogenous compounds that make up part of the structure of DNA and RNA. They are represented by the letters A, T, C, and G
What are carriers?
Individuals who are heterozygous for a recessive allele linked to a genetic disorder. Carriers have one healthy allele so are not affected themselves, but can pass on the affected allele to their offspring
What is cystic fibrosis?
An inherited disorder that affects lungs, digestive, and reproductive system and is inherited through a recessive allele
What is a dominant allele?
The phenotype will be apparent in the offspring even if only one of the alleles is inherited
What is genetic engineering?
The process by which scientists can manipulate and change the genotype of an organism
What is a genotype?
The genetic makeup of an individual for a particular characteristic, for example hair or eye colour
What is a heterozygote?
Individual with different alleles for a characteristic
What is a homozygote?
Individual with different alleles for a characteristic
What is meiosis?
2 stage process of cell division that reduces the chromosome number of daughter cells. It is involved in making gametes for sexual reproduction
What is a mutation?
A change in the genetic material of an organism
What is natural selection?
The process by which evolution takes place. Organisms produce more offspring than the environment can support. Only those that are most suited to their environment will survive to breed and pass on their useful characteristics to their offspring
What is a nucleotide?
A molecule made up of a sugar, a phosphate group, and one of 4 different bases. They are key units in the structure of DNA and RNA
What is a phenotype?
The physical appearance of an individual for a particular characteristic
What is polydactyly?
A dominant inherited disorder that results in babies born with extra fingers and/or toes
What is a Punnet square diagram?
A way of modelling a genetic cross and predicting the outcome using probability
What is a recessive allele?
A phenotype that will only show up in the offspring if both of the alleles coding for that characteristic are inherited
What are sex chromosones?
Carry the information that determines the sex of an individual
What is sexual reproduction?
Involves the fusion of male and female gametes producing genetic variation in the offspring
What is reproduction?
The process by which genetic information is passed on from parents to their offspring
What are advantages of a asexual reproduction?
- Partner not required
- Genetically identical offspring (known as clones) meaning there is no genetic variation and therefore desirable characteristic are passed on. This also is an advantage in favourable conditions.
- It is faster and more rapid than sexual reproduction
What are the disadvantages of asexual reproduction?
- Genetically identical offspring (known as clones) meaning there is no genetic variation and therefore undesirable characteristics may be passed on
- Large groups may be susceptible to the same disease, meaning none of the population are immune, causing the entire population to fall ill to the disease. If one organism cannot survive, none can.
What are gametes?
an organism’s reproductive cells, they contain 1 set of chromosomes so can carry only 1 of the 2 alleles that the parent have in their own cells
What are the advantages of sexual reproduction?
*There is genetic variation, therefore if the environment changes, variation gives a survival advantages to the population as some offspring will be able to survive and reproduce. This is known as natural selection
What are the disadvantages of sexual reproduction?
- 2 gametes (from 2 parents) are required. This is less time and energy efficient than asexual reproduction as it takes time and energy to find a mate and spread gametes
How many chromosomes does a human have?
46 (23 pairs)
How many chromosomes does a human gamete have?
23
What is a gene?
a small section of DNA on a chromosome that codes for a particular sequence of amino acids, to make a specific protein
Describe where to find a gene if you begin outside the cell
Inside the cell there is a membrane bound organelle called the nucleus. Inside the nucleus there are chromosomes. These Chromosomes are thin strands of DNA. Small sections of the DNA are known as genes.
What does the base A pair with?
T
What does the base T pair with?
A
What does the base G pair with?
C
What does the base C pair with?
G
How do the 4 bases in DNA combine?
Complementary base pairing
How many bases code for a particular amino acid?
A sequence of 3 bases in the gene code for a particular amino acid
What do the order of the bases in DNA control?
The order of the bases controls the order in which amino acids are joined together to form a certain protein
What do the sections of DNA that do not code for proteins do?
The non-coding parts of DNA switch genes on and off, they control whether or not a gene is expressed (used to make a protein)
What is a mutation?
A change in the order of the bases that causes the wrong protein to be made
What is the structure of DNA?
The long strands of DNA are made of alternating sugar and phosphate sections. One of 4 basses - A, C, G, T - is attached to each sugar. Each unit containing a sugar, a phosphate, and a base is called a nucleotide. The 2 strands of DNA run in opposite directions and interwind to form a double helix structure
What is protein synthesis controlled by?
The DNA in the nucleus
What are the 2 steps of Proteins Synthesis?
Transcription
Translation
Describe the process of protein synthesis:
The DNA is too large to leave the nucleus (protein synthesis occurs in ribosomes outside of the nucleus), so a template of the gene for the protein is created. This template is known as mRNA and reflects the sequence of bases in the DNA, but it is small enough to leave the nucleus through the pores in the nuclear membrane as it is only a single strand and a single gene. The mRNA then leaves the nucleus through a pore in the nuclear membrane and binds to a ribosome in the cytoplasm
The cytoplasm contains carrier molecules (tRNA), that each carry a specific amino acid. The carrier molecules also contain 3 bases that are complementary to a specific triplet of bases of the mRNA. The corresponding carrier molecule attaches itself to the template. Further Carrier molecules attach themselves to the template in the order given by the DNA. The amino acids they carry join together to form a specific protein chain. Carrier molecules keep bringing specific amino acids to add to the growing protein chain in the correct order until the template is completed. The protein chain detaches from the carrier molecules and the carrier molecules detach from the template and return to the cytoplasm to pick up more amino acids
Once the protein chain is complete, the molecule folds up to form a unique shape that will enable it to carry out its functions in the cell