Reproduction and DNAAQA GCSE Biology: Flashcards

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Define sexual reproduction.

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Define sexual reproduction.: Sexual reproduction involves the fusion of two gametes (sex cells) from two different parents, producing offspring with genetic material from both parents.
Define asexual reproduction.: Asexual reproduction involves a single parent producing genetically identical offspring without the fusion of gametes.
State two advantages of sexual reproduction.: Produces genetic variation in offspring, increasing adaptability to environmental changes. 2. Allows beneficial genes to combine, improving survival chances of the population.
State two disadvantages of sexual reproduction.: Requires two parents, which is time-consuming and energetically costly. 2. Genetic variation may produce less well-adapted offspring.
State two advantages of asexual reproduction.: Only requires one parent, so it is faster and more energy-efficient. 2. Produces genetically identical offspring that are well-adapted if the parent is suited to the environment.
State two disadvantages of asexual reproduction.: Produces genetically identical offspring with no variation. 2. The population cannot adapt if environmental conditions change.
Explain why sexual reproduction produces genetic variation.: Sexual reproduction involves the fusion of gametes from two different parents. During meiosis, crossing over and random assortment of chromosomes create different combinations of alleles. When gametes fuse randomly during fertilisation, this produces offspring with different genetic combinations.
Explain why asexual reproduction produces genetically identical offspring.: Asexual reproduction involves mitosis, which produces exact copies of the parent cell's DNA. Since there is no fusion of gametes and no variation in the copying process, all offspring are clones with identical genes to the parent.
Describe the structure of DNA.: DNA is a double helix composed of two strands of nucleotides twisted together. Each strand runs in opposite directions (antiparallel). The nucleotides are held together by covalent bonds between the sugar and phosphate groups, forming the sugar-phosphate backbone. The two strands are held together by hydrogen bonds between complementary bases.
Name the three components of a nucleotide.: A five-carbon sugar (deoxyribose in DNA). 2. A phosphate group. 3. One of four nitrogenous bases (adenine, thymine, cytosine, or guanine).
State the complementary base pairing rule.: Adenine pairs with thymine (A-T) using two hydrogen bonds. Cytosine pairs with guanine (C-G) using three hydrogen bonds.
Define a gene.: A gene is a sequence of DNA bases that codes for a specific sequence of amino acids to produce a particular protein.
Explain the process of transcription.: Transcription occurs in the nucleus. The DNA double helix unwinds. RNA polymerase binds to the promoter region and reads the template strand of DNA. Free RNA nucleotides bond to complementary bases on the template strand (A pairs with U, not T), forming a molecule of messenger RNA (mRNA). The mRNA is released from the DNA and leaves the nucleus.
Explain the process of translation.: Translation occurs at the ribosome. The mRNA attaches to the ribosome and is read in codons (groups of three bases). Transfer RNA (tRNA) molecules bring the correct amino acids to the ribosome, matching their anticodon to the codon on the mRNA. The amino acids are bonded together in the order specified by the mRNA sequence, forming a protein chain.
Define a codon.: A codon is a sequence of three bases on mRNA that codes for one specific amino acid. This is called a triplet code.
Describe the Human Genome Project and state two potential benefits.: The Human Genome Project was an international research effort that identified and mapped all approximately 20,000 genes in the human genome, sequencing all 3 billion base pairs. Benefits include: 1. Identifying genes responsible for genetic diseases, enabling development of treatments and cures. 2. Enabling personalised medicine based on an individual's genetic profile. 3. Improving understanding of human evolution and diversity.