Читать книгу Lifespan Development - Tara L. Kuther - Страница 146

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Mitosis:

1. Interphase. Chromosomes replicate.

2. Prophase. Chromosomes become visible.

3. Metaphase. Chromosomes line up individually at metaphase plate.

4. Anaphase. Sister chromatids separate, creating two identical daughter cells with 2n chromosomes.

Meiosis:

Meiosis I:

1. Interphase. Chromosomes replicate.

2. Prophase I. Homologous chromosomes undergo synapsis and crossing over occurs.

3. Metaphase I. Chromosomes line up by homologous pairs at metaphase plate.

4. Anaphase I. Homologs separate, creating daughter cells of Meiosis I.

Meiosis II:

5. Anaphase II. Sister chromatids separate, creating daughter cells of Meiosis II. Each daughter cell has 1n chromosome.

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The father has an X and a Y chromosome. The mother has two X chromosomes. Each son has one X and one Y chromosome. The X chromosome was inherited from the mother. The Y chromosome was inherited from the father. Each daughter has two X chromosomes. One X chromosome was inherited from the mother. The other was inherited from the father.

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A father and mother, both with brown hair, have four children. Three have brown hair and one has red hair.

Parent genotype: capital N, lowercase r for both parents.

Child genotype:

1. Son with brown hair: capital N, capital N. He received the dominant gene from both his father and mother.

2. Daughter with brown hair: capital N, lowercase r. She received the dominant gene from her mother and the recessive gene from her father.

3. Second daughter with brown hair: capital N, lowercase r. She received the dominant gene from her father and the recessive gene from her mother.

4. Daughter with red hair: lowercase r, lowercase r. She received the recessive gene from both her father and mother.

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For both examples, the mother, father, and offspring are represented as either black or white silhouettes.

Example 1: Abnormal chromosome arises from the father. The father, shaded black, and the mother, shaded white, have two children: one boy, shaded black, and one girl, shaded black.

Example 2: Abnormal chromosome arises from the mother. The father, shaded black, and the mother, shaded white, have two children: one boy, shaded white, and one girl, shaded white.

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The following attributes are shown or described on the illustration of the child:

Slower growth

Intellectual disability

Flat back of head

Small ears

Short nose

A single line across the palm of the head (palmar crease)

Intestinal blockage

Poor muscle tone or loose joints

Shorter in height as children and adults

Broad, flat face

Almond-shaped eyes that slant up

Small and arched palate

Big, wrinkled tongue

Dental anomalies

Short and broad hands

Congenital heart disease

Enlarged colon

Big toes widely spaced

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Three genotypes are shown, labeled A, B, and C. For each genotype, there is a different range of reaction possible. In this example, the range relates to intelligence performance (IQ). If the person’s environment is deprived, the genotype achieves only the lowest range of reaction. If the person’s environment is average, the genotype achieves only the middle range of reaction. If the person’s environment is enriched, the genotype achieves the highest range of reaction.

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Active gene–environment: Low degree of influence in infancy. Sharp increase to medium to high level in childhood, followed by slower increase throughout adolescence and adulthood, ending with a high level in adulthood.

Evocative gene–environment: Medium degree of influence across all stages.

Passive gene–environment: High degree of influence in infancy, with a sharp decline throughout adolescence, reaching a level of medium to low. The degree of influence continues to decrease throughout adolescence and adulthood, ending with a low level in adulthood.

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A line is shown to the side of each bidirectional influence listed. On each line there are a series of arrows. The arrows are shown in a repeating pattern of one arrow pointing diagonally up to the next line and the next pointing diagonally back down.

Below the graphic is a right-pointing arrow that extends the width of the lines above. The label reads Individual Development.