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There are variations in this gene called alleles. Notes || Questions by Topic This topic is included in Paper 1 , Paper 2 , Paper 3 , Paper 4 , Paper 5 and Paper 6 for IGCSE CIE Biology Marks: 1 Most of the questions are for self-assessment.

Marks: 1 One of the pairs of chromosomes codes for sex inheritance. Our online Biology Bridging the Gap course on 22-23 August can help the transition from GCSE if you are about to start your A-levels. This is because females have two X chromosomes (XX).The normal colour vision allele dominates the abnormal allele, so as long as the female has one normal X chromosome then they will have good colour vision. Marks: 1 Meiosis is a type of nuclear division giving rise to cells that are genetically different. Hard This base sequence within the gene codes for the specific types and order of amino acids that become joined to form a protein. One allele for this gene may code for brown eyes, whereas another allele may code for blue eyes. Cells like this are called diploid cells, and are majority of the cells in the human body. DNA held within the nucleus of the cell. In this case, the chance of a blue eyed child is 1/4, and the chance of a brown eyed child is 3/4. This is a reduction division to form haploid cells which produce gametes. This is very important for various bodily functions: Imagine diploid cell A (46 chromosomes) undergoing mitosis. Medium Marks: 1 We adhere to the GDPR and EU laws and we will not share your personal information with or sell it to third-party marketers. Sex linked characteristics are characteristics in which the gene responsible is located on the sex chromosome, and therefore making it more common in one sex than the other. Medium from 46 to 92) in order to maintain the chromosome number after the cell division occurs. Example 1 – Homozygous recessive (bb) X Heterozygous(Bb)Example 2 – Homozygous recessive (bb) vs Homozygous dominant (Bb) Boost your grades with downloadable PDF resources, videos, and courses. The code within that length is ATTCGAA. Marks: 1 The ratio of blue:brown is 1:3 Co-dominance is when a pair of alleles are neither dominant to one another. Marks: 1

Medium Sex inheritance depends on the presence of X and Y chromosomes.The function of DNA is to control cell function by controlling the production of proteins i.e.

This is half the normal amount in order to maintain 46 chromosomes after fertilization. Practise OCR Gateway genes, inheritance and selection sample exam questions for GCSE Biology. Exercises and Discussions. Medium The DNA is made of a double helix backbone, which are connected by pairs of bases. Detailed revision notes on the topic Inheritance & Genetics. As we’ve discussed above, a gene is a particular length of a DNA molecule containing a specific sequence of bases.


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