Genes - idexcel igcse biology

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24 Terms

1

What is a gene?

A length of DNA that codes for a particular protein or characteristic.

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2

What are chromosomes?

Structures made of DNA and proteins found in the nucleus of a cell.

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3

How many chromosomes do humans have?

Humans have 46 chromosomes, arranged in 23 pairs.

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4

What do sex chromosomes determine?

The sex of the individual; Female: XX, Male: XY.

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5

What are alleles?

Different versions of a gene that can occupy the same position on a chromosome.

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6

What is a dominant allele?

An allele that expresses its trait even if only one copy is present.

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7

What is a recessive allele?

An allele that expresses its trait only when two copies are present.

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8

What is genotype?

The genetic makeup of an individual, represented by the combination of alleles.

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9

What is phenotype?

The physical expression or characteristic resulting from the genotype.

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10

What is Mendelian inheritance?

The set of principles established by Gregor Mendel through his studies of pea plants.

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11

What does the Law of Segregation state?

Each parent passes one of their two alleles for each gene to their offspring.

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12

What is a monohybrid cross?

A genetic cross that studies the inheritance of one gene with two alleles.

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13

What is co-dominance?

A situation where both alleles in a heterozygous individual contribute to the phenotype.

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14

What is incomplete dominance?

A situation where the heterozygous phenotype is an intermediate between the two homozygous phenotypes.

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15

What is a mutation?

A change in the sequence of DNA that can alter the function of a gene.

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16

What are sex chromosomes?

Chromosomes that determine the gender of an individual; females have XX and males have XY.

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17

What is cystic fibrosis?

A genetic disorder caused by a recessive allele, leading to thick mucus affecting lungs and digestive system.

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18

What is sickle cell anemia?

A genetic condition caused by a mutation in the hemoglobin gene, resulting in sickle-shaped red blood cells.

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19

What is genetic screening?

Testing individuals for genetic disorders or mutations.

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20

What is genetic engineering?

The manipulation of an organism’s genome using biotechnology.

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21

What are GM crops?

Genetically modified crops that can have improved resistance to pests or diseases.

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22

What are sex-linked traits?

Traits that are carried on the sex chromosomes, often affecting males more due to having one X chromosome.

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23

What is a Punnett square?

A diagram used to predict the outcome of genetic crosses.

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24

What is a pedigree chart?

A diagram used to track the inheritance of traits within a family.

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