(2) Heredity refers to the similarity between parents and children, and variation refers to the difference between parents and offspring. Both parents have a single eyelid, and Xiaoqing has a single eyelid, which reflects the similarity in traits between parents and children, so it is called heredity in biology. Parents have earlobes, Xiaoqing has no earlobes, which reflects the differences between parents and children, so it is called variation in biology.
(3) There are some traits in the offspring that parents don't have, and the new traits must be recessive, and the genetic components of parents are heterozygous; Therefore, Xiaoqing's personality is recessive, and her parents' genetic components are heterozygous. If the earlobe is controlled by a pair of genes (B/b), capital letters represent dominant genes and lowercase letters represent recessive genes. Then the genetic composition of father and Xiaoqing is bb and Bb respectively. The gene map is as follows:
As can be seen from the picture, if Xiaoqing's parents have another child, the possibility of not having an earlobe is 25%.
(4) Capital letters represent dominant genes and lowercase letters represent recessive genes. If the control gene of tongue curl is D and the control gene of tongue curl is D, it means that tongue curl is a dominant trait controlled by Dd or Dd, and tongue curl is a recessive trait. Her genetic makeup is DD. Then the gene combination that determines whether to roll the tongue is: the father can roll the tongue, and there may be two kinds of gene combinations, namely: DD or DD. Mother can't roll her tongue. There is only one gene combination, namely: DD. Xiaoqing's genes are one from her father and one from her mother. Because her mother's gene combination is recessive, Xiaoqing inherited the recessive gene D from her mother, and Xiaoqing's characteristic is that she can roll her tongue. Therefore, no matter what her father's genetic combination is, she must inherit the dominant gene D that can roll her tongue from her father. So Xiaoqing's gene combination is DD.
(5) Xiaoqing's parents have single eyelids, and so do her children. Although Xiao Zhang's mother has become a double eyelid through plastic surgery, her genetic composition will not change, which belongs to genetic variation, so she can't have a child with double eyelids.
(6) During the formation of parental germ cells, after meiosis, chromosomes are separated from each other, and men produce two kinds of sperm-sperm with 22+X chromosome and sperm with 22+Y chromosome, while women only produce one kind of egg cell with 22+X chromosome. If 22+X sperm is combined with the egg during fertilization, 44+XX fertilized eggs will be produced and developed into women. If the sperm containing 22+Y combines with the egg, it will produce a fertilized egg with 44+XY and develop into a male. Because men can produce an equal number of 22+X sperm and 22+Y sperm, and their chances of combining with eggs are equal, the chances of giving birth to boys and girls at one time are equal. The sex ratio of the whole population is roughly 1: 1. Everyone knows Xiaoqing is a girl.
So the answer is:
(1) relative character
(2) heredity; change
(3)Bb； bb； 25%
(4)DD； Deadline Date (abbreviation for deadline date)
(5) no.
(6)50%