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Virginia Tech PSYC 2034 - Reading & Study Guide 2.1

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Section 1Developmental PsychologyReading & Study Guide 2.1Read the specified sections and answer the associated questions. Be sure to use your own words (different from your book and from your friends) when answering. Section 11) How are GENOTYPES and PHENOTYPES different?The genes expressed in every human’s cells are called a genotype. The expressed, physical characteristics of a person are called the phenotype. They are different because of dominant-recessive inheritance, incomplete dominance, and environmental influences. Many characteristics can be influenced by multiple genes instead of just one. 2) Explain how DOMINANT-RECESSIVE INHERITANCE works for straight (recessive) versus curly (dominant) hair.This pattern of inheritance is when a pair of chromosomes contains one dominant and one recessive gene but the phenotype only expresses the dominant gene. In this example, curly hair is dominant over straight hair, therefore curly hair would be expressed in the phenotype.3) Explain what happens to a trait with one dominant allele and one recessive allele when there is INCOMPLETE DOMINANCE. What would happen to the same traitwith one dominant allele and one recessive allele when there is complete dominance?Incomplete dominance is when the phenotype is influenced primarily by the dominant gene but also to some extent the recessive gene. Neither allele is fully dominant nor recessive and both are expressed. Complete dominance is when the allele that is dominant completely masks the recessive allele. The dominant allele will always be expressed.4) What makes SEX CHROMOSOMES different from other chromosomes?These are the chromosomes that determine whether the organism will be male (XY) or female (XX). Unlike the other chromosomes, the sex chromosomes are not identical, the X chromosome is larger and carries more genes than the Y chromosome.5) Why are males more vulnerable than females to recessive disorders that are found on the X chromosome? (X-LINKED INHERITANCE)Males have only one X chromosome compared to females who have two. This makes males much more vulnerable to recessive disorders. This is because if a male receives one X chromosome with a recessive gene for a disorder, he will definitely have theDevelopmental Psychologydisorder because unlike females, he has no other X chromosome that could protect him from inheriting the disorder with a dominant gene. 6) Why are monozygotic twins (MZ), dizygotic twins (DZ), and adopted children useful for helping researchers understand how genes influence our development?Monozygotic twins have 100% of their genes in common. Dizygotic twins have 40%-60% of their genes in common. Adopted children have no genetic resemblance to their adoptive parents. These different groups and their corresponding genes help researchers estimate the influence of genes on our development. Comparing the behaviors of these different twins and adopted children to the genes they have in common with their siblings and parents can help to understand if there is a stronger genetic influence or a stronger environmental influence.7) What is a HERITABILITY ESTIMATE?An estimate of the extent to which genes are responsible for the differences among people within a specific population. It ranges from 0-1.00. Heritability can be used to estimate a wide range of different characteristics such as: intelligence, personality, activity level, sociability, etc. Heritability estimates are not just a measure of genetic influence but of how much the environment allows the genes to be expressed.8) What is a CONCORDANCE RATE?A percentage that indicates the degree of similarity in phenotype among family members. They range from 0% to 100% and the higher the concordance rate, the more similar pairs of persons there are. 9) Explain how genes and the environment interact to affect development. Be sure to use the term REACTION RANGE in your answer.Genes can influence human development by establishing boundaries for environmental influences rather than by specifying a characteristic. The reaction rate can be used to show the possible developmental paths established by genes and the environment shows where those genes will actually show up.10) Explain PASSIVE GENOTYPE � ENVIRONMENT EFFECTS. What does it mean for the genotype to be passive?Passive Genotype ——> Environment effects occur within biological families because parents provide both the genes and environment for their children. In biological families,separating genetic influences from environmental influences can be difficult because they are both provided by the parents.Developmental Psychology11)Explain EVOCATIVE GENOTYPE � ENVIRONMENT EFFECTS. What does it mean for the genotype to be evocative? Evocative genotype——> Environment effects occur when a persons inherited characteristics evoke responses from others in the environment. Meaning that the individual's genotypes influence the responses that they receive from others. 12)Explain ACTIVE GENOTYPE � ENVIRONMENT EFFECTS. What does it mean for the genotype to be active?Active Genotype—-> environment effects occur when people seek out environments that correspond to their genotypic characteristics also called “niche picking”. This is the idea that people are more drawn to environments that match their inherited abilities and special skills. 13)What happens during conception that results in DZ twins? What are the ETHNIC DIFFERENCES in DZ twin rates?During conception, when a woman’s ovary releases two ova instead of one, a the spermfertilize both, DZ twins are created. Meaning that there are two zygotes (dizygotic). This takes place overall 1 in every 60 births however there are ethnic variations such as 1 every 700 births in Japan and 1 every 25 in Nigeria. In general Africans have the highest rates of DZ twins and Asians have the lowest. 14)What happens during conception that results in MZ twins? What are the ETHNIC DIFFERENCES in MZ twin rates?When one zygote splits into two separate clusters of cells, MZ twins are created. Monozygotic twins are less common than DZ twins overall, occurring in about 1 every 285 births. MZ twins are not more common in any specific ethnic groups and they take place at the same frequency all over the

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