After germination, auxin is important in the growth of barley plants. Describe and explain the role of auxin in cell elongation. ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . ............................................................................................................................................... . .........................................................................................................................................

Biology

IGCSE&ALevel

CAIE

Exam No：9700_m24_qp_42 Year：2024 Question No：9(b)

Answer:

Knowledge points:

16.1.1 explain the meanings of the terms haploid (n) and diploid (2n)

16.1.2 explain what is meant by homologous pairs of chromosomes

16.1.3 explain the need for a reduction division during meiosis in the production of gametes

16.1.4 describe the behaviour of chromosomes in plant and animal cells during meiosis and the associated behaviour of the nuclear envelope, the cell surface membrane and the spindle (names of the main stages of meiosis, but not the sub-divisions of prophase I, are expected: prophase I, metaphase I, anaphase I, telophase I, prophase II, metaphase II, anaphase II and telophase II)

16.1.5 interpret photomicrographs and diagrams of cells in different stages of meiosis and identify the main stages of meiosis

16.1.6 explain that crossing over and random orientation (independent assortment) of pairs of homologous chromosomes and sister chromatids during meiosis produces genetically different gametes

16.1.7 explain that the random fusion of gametes at fertilisation produces genetically different individuals

16.2.1 explain the terms gene, locus, allele, dominant, recessive, codominant, linkage, test cross, F1, F2, phenotype, genotype, homozygous and heterozygous

16.2.2 interpret and construct genetic diagrams, including Punnett squares, to explain and predict the results of monohybrid crosses and dihybrid crosses that involve dominance, codominance, multiple alleles and sex linkage

16.2.3 interpret and construct genetic diagrams, including Punnett squares, to explain and predict the results of dihybrid crosses that involve autosomal linkage and epistasis (knowledge of the expected ratios for different types of epistasis is not expected)

16.2.4 interpret and construct genetic diagrams, including Punnett squares, to explain and predict the results of test crosses

16.2.5 use the chi-squared test to test the significance of differences between observed and expected results (the formula for the chi-squared test will be provided, as shown in the Mathematical requirements)

16.2.6.1 TYR gene, tyrosinase and albinism

16.2.6.2 HBB gene, haemoglobin and sickle cell anaemia

16.2.6.3 F8 gene, factor VIII and haemophilia

16.2.6.4 HTT gene, huntingtin and Huntington’s disease

16.2.7 explain the role of gibberellin in stem elongation including the role of the dominant allele, Le, that codes for a functional enzyme in the gibberellin synthesis pathway, and the recessive allele, le, that codes for a non-functional enzyme

Answer:

Knowledge points:

Solution:

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